Translation support for Angular-based pages

This includes a few major pieces:

1. Update the string scanner to support partials/**.html files. Look for expressions like ts('Hello').

2. Update the Angular base-page to transmit localized strings at runtime, i.e.

• Declare a list of *.html files
• When requesting /civicrm/a, send strings for any *.html files.
• Optional: Aggregate the *.html files.