Added first version of 'Plugins' window. It's accessible through 'Edit/Plugins' item in roster menu. It seems that you can successfully (de)activate plug-ins through GUI now.

Added 'homepage' attribute to Plugin class.

Added (commented out) calls of pycallgraph in src/gajim.py for later use.

[xbright] Changed 'python' to 'python2.5' because code uses modules not available in previous versions of Python.