Now only jid-multi isn't handled.

As long as the responder uses only text-single, list-single and
boolean fields, it is possible to invoke and complete a command.
Other field types are not implemented now in dataforms.py.

If the entity has at least one command exposed, it will be displayed as
a radio button. Other changes: run python interpreter without optimalizations,
otherwise asserts doesn't work. Names of widgets in the glade file were
changed a bit.

Added: glade file for commands window, src/adhoc_commands.py with a class
to create/manage the window. For now, progressbar bounces :-).

Introduced a widget that will present full data form as in JEP-0004, to make
things easier. Code will just have to create this widget with just-got
xmpp.DataForm form, show it to user, wait a bit and send the modified form
back.

The fixes:
 * when received a single message from a contact that has one resource online,
   'start chat' entry in popup menu open only that message, not the chat
 * when contact has more resources online, 'rename item' entry in popup menu
   doesn't work