fix(web): toolbar and loading optimisations

There are a number of changes here to improve the performance of
KeymanWeb and the toolbar and reduce unnecessary requests:

1. (kmwbase.ts and kmwkeyboards.ts) Added option `setActiveOnRegister`,
   default `'true'`; if set to `'false'` then will never attempt to
   activate the first registered keyboard. Note that this property is a
   string because the `options` object currently supports only string
   types, which is not ideal, but out of scope for this PR.

2. (kmwuitoolbar.ts) fixed issue with toolbar not matching correctly on
   full BCP 47 code (line 960) after keyboard change notification.

3. (kmwuitoolbar.ts) fixed issue with toolbar not showing active
   keyboard if the keyboard is activated before init is complete
   (see `ui.lastSelectedKeyboard` references).

4. (kmwuitoolbar.ts) avoided re-entrancy for `ui.changeKeyboardEvent`
   by ensuring that `ui.selectKeyboard` does not attempt to set the
   active keyboard again for keymanweb; note that this was being caught
   by the event dispatcher in keymanweb but it was still not ideal.

5. (kmwuitoolbar.ts) with above changes, able to remove appalling two
   second timeout on load (yay!)

These changes will be useful immediately with keymanweb.com.