Remove logging from unhandled messages.

Some messages are handled in the browser action, not background page,
so it doesn't make sense to log 'unknown extension message' for them.
Populate the Report Issue box before showing it. Switch to sliding instead of toggling.
Fix the translated strings for the term “Calendars” used on the Options page
New Cards UI visual design.
Use the browser's language for Moment.js

Regression caused while upgrading Moment.js version.
Update error handling code to account for new DOM
Show a card action, “View on Map” for events with locations.