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
Move groups fixture to core app, where it belongs
Load default permission groups during installation
Fix mailto link for gym email
Update gitignore file