adding a way to destroy a room

[misc]

xep 0045, on http://www.xmpp.org/extensions/xep-0045.html#destroyroom, say that a owner can destroy a room. It would be nice to have such item in the menu for groupchat ( the one with history, change nickname, etc ).

[asterix]

(In [8010]) ability to destroy a room when we are owner, give a reason and alternative room jid. fixes #3031

[anonymous]

(gajim:20005): libglade-WARNING **: could not find glade file '../data/glade/dubbleinput_dialog.glade'
Traceback (most recent call last):
  File "/home/st/projekte/python/gajim/src/groupchat_control.py", line 1460, in _on_destroy_room_menuitem_activate
    _('You may also enter an alternate venue:'))
  File "/home/st/projekte/python/gajim/src/dialogs.py", line 1059, in __init__
    self.xml = gtkgui_helpers.get_glade('dubbleinput_dialog.glade')
  File "/home/st/projekte/python/gajim/src/gtkgui_helpers.py", line 57, in get_glade
    return gtk.glade.XML(file_path, root=root, domain=i18n.APP)
RuntimeError: could not create GladeXML object

I get the error above, when i try to destroy a room. In addition you may want to change "Delte room" to capitol letters like in the other menuitems.

[asterix]

(In [8011]) add missing file to previous commit. fixes #3031