Emptying the resources array when the resource is null

We remove the offline state as a choice in the dropdown because
'offline' is not a valid XMPP state and it doesn't propagate across tabs.

Updates: #547

Two new configuration settings: locked_domain and default_domain.

(when user manually scrolled up).

Updates #352

Updates #521 and #536.

Turn the logic around so that a presence stanza is always sent out, except in
the single case where we know for sure that the session was restored, in which
case a presence stanza is not required becaus we "never left".

Should already have been removed in the previous release.

Make sure to send out a presence stanza when one of the following:
1. The connection dropped and the user logged in again
2. Websockets are used (each session is established anew)
3. Keepalive isn't being used in BOSH (each session is established anew).

Also add an introductory section on debugging.

Auto join on invite patch 1 (auto_join_on_invite new parameter)

no-otr compilation issue: Utils is not defined

Updated Hungarian translation

Added the remaining untraslated strings, and also fixed some mistakes in
the translated ones.

Optimized some translations

- The .box-flyout container also needs it's width set upon page load.
- Remove custom height/width upon viewport change (if viewport is small enough).

Compare bare JID of from attr in roster update. @teseo's fix was too specific
and tailored for a misbehaving server (servers shouldn't be sending from the
full JID in a roster push).