Overhaul of UI

I have completely redone the how gmail-crypt is integrated into gmail to make it fit in much more cleanly. I have also rewritten gmail-crypt.js so that all code is contained within a closure and is nicely object oriented.

Also I have added a password store which stores the users password for a configurable amount of time (0 to 30 mins) so they don't have to constantly re-enter their password. The store is kept as a private object within the gmail-crypt object so malicious code can not access the password for themselves.