Use getIntuition() to allow multiple modules to share 1 async instance
Use mw.user.getRights instead of fetching directly

This allows multiple gadgets to share the same request instead
of all fetching it independently.

Also cleaned up ugly logic as remnant of using XML.
Remove unused `userHasDeletedhistoryRight` variable
Fix selector strength of mw-rtrc-item subclasses

Follows-up 4eccb49.
Refactor time offset logic

Get it from the user preferences instead of siteinfo API.
Native interfaces also use user preferences instead of the
site-wide setting for this.

As wikiid (also fetched from siteinfo API) can be retreived
from mw.config, this means we can remove the siteinfo API
request.
Rewrite init procedures

Now promise-based and better utilising parallelisation.

Added missing dependency on 'mediawiki.user'.

Removed IE8 condition and usage of 'jquery.client' module that
was also missing from the dependencies. There is now a feature
test for Date.UTC. Everything else should be fine even in
IE7 thanks to jQuery.

Browsers not supporting jQuery are already filtered out by
MediaWiki's startup module.
Implement support for rctag option

Fixes #19.