Use Special:MobileLanguages in beta/alpha

Don't load langlinks when initially loading the
page; instead, wait until button is pressed.

If JavaScript is available, load the langlinks via
the api and then show a LanguageOverlay; if not, just
link to Special:MobileLanguages.

Also remove now-unneeded parseList() function and associated
tests.

This is all done in beta (when it goes stable, there are
redundant functions that should be removed and have been
marked as such).

Bug: 40678
Change-Id: I7d5f2fa9c6d30fe2f2ca2d194f6ecbe72b02c88b
Merge "Use Special:MobileLanguages in beta/alpha"