User Profile solved merging problem

After updated to the last version in Codalab, the South migration for
web application give an error for older migrations. Solved cleaning old
migrations and creating a newer one.
User Profile

Changed base template to use the user profile image instead of the
empty profile image.
User Profile

Modified the URLs to allow call the visualization view with parameters.

Added a non modification view for any user, which can be integrated in
other parts of Codalab to show user profile. By the moment the basic
information is shown and the list of competitions are optional.
Teams Management

Created team application in CodalabProject. Added the models for teams
and membership, considering than:
- One user can be in many teams.
- One team have many users.
- A team can invite a user to be a member, and the user may  decide if
accepts or not.
- A user can request to be member of a team, and the team may decide if
accepts or not.
- A team exists apart from the competitions.
- A team can have multiple administrators.