Friends functionality

Dear Colleagues, Hi!

I've added a friends functionality yesterday. From now on you can mark other user's profiles by adding them to your friends. This relation is one-directional (so that to create bi-directional "friendship" both people should participate).

Besides seeing other's people public friend lists, you will be also able to see ranking for your friends only (probably this could be usable as the total amount of users grow) - you need to visit Ranking page and click View Friends here.

The design is not very cleverly-thought-of right now, sory - but I'll improve it by and by. Please report any bugs or suggestions freely!