Consolidate localization behavior and init to a coreLocalizer function and singleton
Explicitly support `en-US` locale
Rename coreData to coreFileFetcher and export a singleton rather than using a property of coreContext
Add `apiConnections` property of coreContext to simplify adding a source switcher
Replace some init functions with re-callable, promise-supporting `ensureLoaded` functions
Make coreContext itself load the UI if a container has been specified at init time
Fix code tests
The idea here is that the validator will now hold onto lots of issues,
but the calling code will only want some small subset of them
(edited/everything) (inview/everywhere) and can pass these as options
so that we don't need filtering code spread throughtout the app.
Rename IssueManager to coreValidator
Rename disconnected highway to disconnected way
Rename highway almost junction to almost junction
Rename mapcss checks to maprules
Rename deprecated tags to deprecated tag
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
