User profile basics

Shows a basic user profile page.
* Bring in some decorators from OTM2 (they will disappear when we switch to `django-tinsel`
* Show/hide sections based on user's privacy settings and whether viewing user's own profile
* Empty sections for Contributions, Achievements, and Groups (collapsible pending Bootstrap)

NOTE: I mistakenly pushed to `develop` (without a PR) a commit with initial migrations. Make sure to run `migrate`.

Tests forthcoming (I wanted to get this up to allow working on sections of the profile page).