Remove unused parts of profiles app

This will ease the task of moving used parts to the accounts app.

We kept all profiles app code around, without any changes besides
those strictly required to support Django 1.5+, to allow easy upgrade
by using diff to see the differences in the code, but now is no longer
necessary.
Move profile_tags template tags to accounts app
Profile views: Call the view directly, without any alias
Profile views: Move all profile URLs to accounts app
Profiles: sanitized URL pattern name
User: converted profile edit view into a CBV

This implies getting rid of pootle_profile app
User: adjusted profile views

As a result the profiles app was wiped out
Settings: Remove remnant of pootle_profile

Not sure if this is a good idea.
Bugfix: Make migration run in MySQL as well
Simplify account migration

Might take more time to run, but code is simpler to understand.