User authorization.

This adds user authorization to the user pages and fixes #29.

Regular users can:
- View their own profile.
- Edit their own profile.
- View their own orders.
- Delete their profile.
- Can add a subscription to themselves.

Admin users can:
- Retrieve list of all users.
- Search for users.
- View any user.
- View any user's orders.
- Edit any user.
- Delete any user profile.
- Can add a subscription to any user.

CC: @mex