create branch for "voting" feature

(I also did some clean up, just to have something to commit)
add 'django-voting' code; add it to INSTALLED_APPS
give up 'django-voting'

I can't understand it, neither make it work. Should we make it
ourselves? Using Forms+Urls.py+AJAX ?
give up 'django-voting'

I can't understand it, neither make it work. Should we make it
ourselves? Using Forms, Urls.py and AJAX?
code cleanup and basis for voting

Proposal's 'id' is now called 'id_num' (like Person). Code and
documentation cleanup. Created class "ProposalVote" to store votes.
Added fix_djangoORM with SQL commands to fix the limitations of Django's
ORM (doesn't provide "composite primary keys").
add basic voting functionality

You can vote once without being registered; ProposalVote table now has
one PrimaryKey (an id) instead of two ForeignKeys (it's simpler for
now); Switched from 'form' button to 'a' button to cast vote;
enforce that ProposalVote's ForeignKeys are unique
Merge remote-tracking branch 'origin/diogo_voting'

Conflicts:
	parliament/models.py
	parliament/views.py
	templates/parliament/proposal_detail.html

git merge diogo_voting
git push origin master