Update `text` functions to `html` to support inserting the `span` elements
Specify `html: false` for various instances where a `span` is not desired, e.g. `placeholder` and `title` attributes
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
- ES6ify (now using class syntax to define QAItem objects)
- Fix bug with KeepRight marker rendering not updating properly
- Use `qa-` prefix for the UI element classes to differentiate from iD
validation error related UI element classes
- Move away from "error" where possible in source
- Move away from snake_case naming where possible
Note that some function/method names have been untouched to make life
easier for v3 development. Have added note comments where appropriate.
Filters out errors not present in the data .json file to enable
selective support since Osmose has a wide variety of errors which may be
too advanced for iD.
Also added processing for the elements associated with an error for
forced visibility and highlighting.
