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
Because notes dont exist in the history or graph, there is no history change
event to trigger a redraw, as there would be when adding points and other things.
Also stringify the note id (because existing notes from OSM are this way)
Also make sure comments is initialized as an Array not an Object
Also clarify some of the tests
