Change secure login to use a user preference

Removed the wpStickHTTPS checkbox from the login form, and instead
just use the user's preferences along with whether they came from
HTTPS or not to determine if they should stay in HTTPS.

Bug: 29898
Bug: 52283
Change-Id: I69e9cb23b8d700e821b8a961c672958e4e19e4f8
Merge "Change secure login to use a user preference" into wmf/1.22wmf12