Added authenticator for Iodine

Uses the native accounts APIs, thus replacing the previous CookieStore
mess. Cool! LoginActivity is now IodineAuthenticatorActivity.

Also a few other random changes, bleh bleh, that's why the version is
still 0.1 and probably will be until something releasable is produced.

Having two AccountAuthenticators is a mess and I might do something
about that in the future.