This makes the code a bit more consistent and lets us avoid some
hacky and probably non-performant things:
- abusing CSS classes in the draw/drag datum functions (classed `.target`)
(is this thing target? just check d.properties)
- regexing the id for `-nope$`
(is this thing a nope target? just check d.properties)
- using context.hasEntity to get a the real entity
(is this thing a real osmEntity? just check d.properties)
- fixes code like the restriction editor which uses fake ids for split ways
Mouseup was turning into a click on whatever was the last thing clicked.
In this walkthrough, this would sometimes be the "Add Area" mode button,
which would re-enter the add area mode and throw away the user's drawing.
(I have no idea why.)
(closes#3986)
Root cause was the vertex shadow strokes were too big, esp on endpoints.
For normal lines 16px stroke width centers on the line, but for vertices
it extends beyond the vertex radius, stealing clicks.
Also switched some "globals" to module variables in draw.js
