fixed lock icon when session has been terminated

(Tooltips might not be complete because of some not yet addressed backend bugs)

This fixes a bug with metacontacts over different groups and should stop contact duplication in most cases.

thread id, but to even remove the lock symbol when OTR was ended
and we don't have a thread id.

Whenever we write to the underlying child_model gtk will call the _visible_func on itself.

when that event is received and the lock icon updated.

 * use correct API in session.py
 * only filter when really needed

  tag to outgoing messages anymore. Messages are not even passed to
  libotr anymore then.
* If we don't support OTR, strip OTR tags from the message before
  displaying it.

* Don't set encrypted = True if it was only a tagged plaintext msg.

* Don't include docutils stuff in win32 builds.

or less a workaround. We never let libotr handle unencrypted messages
now and handle notifying the user about the message not being encrypted
ourself.

Correct some bugs with the name used to create a MUC from a 1-to-1 chat when the server can't send a unique key. See #2095.

correct. Adjust tooltips to that.