Extend data model for validation issues

Add the Issues pane

1. Add a class to represent the validation issue
2. Extend the data model for an validation issue to
  (1) add a severity level field (useful for identify save-blocking issues later)
  (2) replace single entity with an array of entities (useful for issues involving multiple entities)
  (3) add a coordinates field for highlighting the location of the issue on the map
  (4) add a fixes field for possible automatic fixes

3. Update existing validation modules to use the new data model

dist/locales/en.json

@@ -7579,9 +7579,6 @@
             "SPW_PICC": {
                 "name": "SPW(allonie) PICC numerical imagery"
             },
-            "US-TIGER-Roads-2012": {
-                "name": "TIGER Roads 2012"
-            },
             "US-TIGER-Roads-2014": {
                 "description": "At zoom level 16+, public domain map data from the US Census. At lower zooms, only changes since 2006 minus changes already incorporated into OpenStreetMap",
                 "name": "TIGER Roads 2014"
@@ -7590,6 +7587,10 @@
                 "description": "Yellow = Public domain map data from the US Census. Red = Data not found in OpenStreetMap",
                 "name": "TIGER Roads 2017"
             },
+            "US-TIGER-Roads-2018": {
+                "description": "Yellow = Public domain map data from the US Census. Red = Data not found in OpenStreetMap",
+                "name": "TIGER Roads 2018"
+            },
             "US_Forest_Service_roads_overlay": {
                 "description": "Highway: Green casing = unclassified. Brown casing = track. Surface: gravel = light brown fill, Asphalt = black, paved = gray, ground =white, concrete = blue, grass = green. Seasonal = white bars",
                 "name": "U.S. Forest Roads Overlay"
@@ -7606,6 +7607,12 @@
                 },
                 "name": "UrbIS-Ortho 2017"
             },
+            "UrbISOrtho2018": {
+                "attribution": {
+                    "text": "Realized by means of Brussels UrbIS®© - Distribution & Copyright CIRB"
+                },
+                "name": "UrbIS-Ortho 2018"
+            },
             "UrbisAdmFR": {
                 "attribution": {
                     "text": "Realized by means of Brussels UrbIS®© - Distribution & Copyright CIRB"
@@ -7690,11 +7697,33 @@
                 "description": "Japan GSI Standard Map. Widely covered.",
                 "name": "Japan GSI Standard Map"
             },
-            "hike_n_bike": {
+            "helsingborg-orto": {
                 "attribution": {
-                    "text": "© OpenStreetMap contributors"
+                    "text": "© Helsingborg municipality"
                 },
-                "name": "Hike & Bike"
+                "description": "Orthophotos from the municipality of Helsingborg 2016, public domain",
+                "name": "Helsingborg Orthophoto"
+            },
+            "kalmar-orto-2014": {
+                "attribution": {
+                    "text": "© Kalmar municipality"
+                },
+                "description": "Orthophotos for the north coast of the municipality of Kalmar 2014",
+                "name": "Kalmar North Orthophoto 2014"
+            },
+            "kalmar-orto-2016": {
+                "attribution": {
+                    "text": "© Kalmar municipality"
+                },
+                "description": "Orthophotos for the south coast of the municipality of Kalmar 2016",
+                "name": "Kalmar South Orthophoto 2016"
+            },
+            "kalmar-orto-2018": {
+                "attribution": {
+                    "text": "© Kalmar municipality"
+                },
+                "description": "Orthophotos for urban areas of the municipality of Kalmar 2018",
+                "name": "Kalmar Urban Orthophoto 2018"
             },
             "kelkkareitit": {
                 "attribution": {
@@ -7717,6 +7746,20 @@
                 "description": "Mosaic of Swedish orthophotos from the period 1970–1980. Is under construction.",
                 "name": "Lantmäteriet Historic Orthophoto 1975"
             },
+            "lantmateriet-topowebb": {
+                "attribution": {
+                    "text": "© Lantmäteriet, CC0"
+                },
+                "description": "Topographic map of Sweden 1:50 000",
+                "name": "Lantmäteriet Topographic Map"
+            },
+            "linkoping-orto": {
+                "attribution": {
+                    "text": "© Linköping municipality"
+                },
+                "description": "Orthophotos from the municipality of Linköping 2010, open data",
+                "name": "Linköping Orthophoto"
+            },
             "mapbox_locator_overlay": {
                 "attribution": {
                     "text": "Terms & Feedback"
@@ -7781,6 +7824,13 @@
                 },
                 "name": "Stamen Terrain"
             },
+            "stockholm-orto": {
+                "attribution": {
+                    "text": "© Stockholm municipality, CC0"
+                },
+                "description": "Orthophotos from the municipality of Stockholm 2015, CC0 license",
+                "name": "Stockholm Orthophoto"
+            },
             "tf-cycle": {
                 "attribution": {
                     "text": "Maps © Thunderforest, Data © OpenStreetMap contributors"