Because SHA-1 is not really relevant anymore.
Too bad it's significantly longer and tiring to check, even if that is
to be expected.

For example, a tab can be named muc.example.com, if you do /list
muc.example.com.  If you then do /join muc.example.com, the error handler
needs to get the correct tab (the MucTab, not the MucListTab previously
opened).
This commit fixes the above issue (a traceback), and maybe some others like
that.

happens when beep_on contains "message".

thanks eijebong

(keep a get_name() fallback just in case for now)

some stuff is now hidden wen the window size gets too small (might need
some adjustments). The info buffer in the roster tab, the userlist in
mucs, the vertical tab list, the info buffer everywhere, etc…

xmpp.plugin['xep_0030'].has_identity appears to be unreliable at best,
so we provide our own.

Might help the case of carbons not displayed.

- two options request/ack_message_receipts
- two new theme parameters : CHAR_ACK_RECEIVED and COLOR_CHAR_ACK
- if a message has a receipt, the character is displayed between the
  timestamp and the nick, using the color

- fix the bug where messages from our own jid were incorrectly displayed
- the nick is now fixed for the whole conversation

- add a show_composing_tabs option, default value: "direct"
- todo: find a nice different color for this

- fallback to mediated invitations if only the bare jid is given to the
  command or if the jid does not advertise support

TODO: provide a way to send passwords

fixes whitespace issues, some builtin overrides, and some enormous lines

might make poezio run nanoseconds faster!

Although the logic stays the same, and everything is put back together
in a single class.