Support for DBUS-less mode.

[Gilboa Davara <gilboad gmail com>]

Hello,

When trying to used meld to compare files as root, I'm getting exceptions due to meld being unable to connect to DBUS (access denied).

(meld:29000): GConf-WARNING **: Client failed to connect to the D-BUS daemon:
Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
Traceback (most recent call last):
  File "/usr/bin/meld", line 154, in <module>
    main()
  File "/usr/bin/meld", line 136, in main
    import meld.meldapp
  File "/usr/share/meld/meld/meldapp.py", line 216, in <module>
    app = MeldApp()
  File "/usr/share/meld/meld/meldapp.py", line 113, in __init__
    self.prefs = preferences.MeldPreferences()
  File "/usr/share/meld/meld/preferences.py", line 259, in __init__
    super(MeldPreferences, self).__init__("/apps/meld", self.defaults)
  File "/usr/share/meld/meld/util/prefs.py", line 93, in __init__
    self._gconf.add_dir(rootkey, gconf.CLIENT_PRELOAD_NONE)
glib.GError: No D-BUS daemon running

Any chance of making meld simply disable dbus support when dbus is unavailable?

- GIlboa