Merge pull request #9 from boudewijn-tribler/devel

Performance improved with new _iter_category and _iter_categories method...
Using git makes revision.py obsolete.
Merge pull request #14 from boudewijn-tribler/devel

Using git makes revision.py obsolete.
Merge remote-tracking branch 'remotes/upstream/devel' into origin-stop

Conflicts:
	database.py
	member.py
	script.py
	singleton.py