Add support for gym management
Fix accessing the user data as a gym manager
Fix regular expression used to create new users
Save only the user pk to the session

For security reasons, Django 1.6 defaults to using a JSON serializer so
saving user objects to the session is not possible.
Add links to the user's gym
Move site administration options to user dropdown
Remove unused CSS classes for the mobile version
Add tests for the trainer user switching
Add missing migration files
Show the gym's data on its detail page
Add system wide gym configuration options

At the moment this only allows the administrator to set a default
gym for the installation.
Use the models' get_abolsute_url to specify the success URL
Split gym member list into admins and regular users
Show number of members in current gym
Only logged in users can acces the user detail page

While it was already not possible before to access the page, an exception was
raises as unauthenticated users don't have a userprofile
Use nested namespaces for gym URLs

See #92
Commit missing fixture for global gym configuration
Filter out admin links by checking individual rights
Check for specific permissions in language views
Update default 'admin' permission group