Example plug-ins were modified to use init() instead of __init__().
Added new category in configuration - 'plugins'. It only holds one option for each plugin - 'active', which determines whether plugin should be activated on startup.
Now, Gajim remembers which plugins are active on exit, and activates them on next startup.
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.