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
Also dist/data/* contains minified files now
These are now external and will fetch as needed:
-export { dataAddressFormats } from './address-formats.json';
-export { dataDeprecated } from './deprecated.json';
-export { dataDiscarded } from './discarded.json';
-export { dataLanguages } from './languages.json';
-export { dataPhoneFormats } from './phone-formats.json';
-export { dataShortcuts } from './shortcuts.json';
-export { dataTerritoryLanguages } from './territory-languages.json';
