Engine(-XMPP), Frontend-GNOME: updating a tab's title was not possible, but required for xmpp person chats

previously this was done by removing the chat and adding a new one
Merge pull request #122 from oli-obk/chatmodel_set_name
Engine-XMPP: display preferred nickname as local echo name
Engine-XMPP: forgot to rejoin chatrooms and reenable private chats on reconnect
Merge pull request #154 from oli-obk/fix/reenable_on_reconnect
Engine-XMPP: unknown muc error messages got swallowed silently
Engine-XMPP: send preferred nickname to contacts
Engine-XMPP: nicknames from contacts were ignored

when a nickname is received, the roster name of the contact is updated
Engine-XMPP: nickname changed messages did not appear in ContactChat anymore
Merge pull request #152 from oli-obk/fix/muc_error_messages
Merge pull request #153 from oli-obk/feature/nickname
Engine-XMPP: regression from fc69d82cead caused NRE when sending messages to bare Jids

this was noticed in gtalk, as messages there are always sent to bare Jids.
calling /whois on a contact to which such a message had been sent caused the NullRefException.
this will be properly fixed in refactor/XmppResourceModel
Frontend-GNOME: fixed imperfect topic height
Merge branch 'stable'
Frontend-GNOME: fixed typo in variable name which broke the build
Merge branch 'stable'
Merge pull request #155 from oli-obk/fix/regression_send_message
L10N: remove auto generated smuxi-engine-twitter.pot
L10N: fixed typo in variable name
Transifex: added new translation domains smuxi-engine-(jabbr|xmpp) and smuxi-frontend-gnome-(twitter|xmpp)