Public profile pages and basic contribution management

[nitinseshadri]

This PR adds the following:

• Public profile pages, viewable by going to /user/profile/<username> or /user/profile/<uuid>, or, to view their own profile, users can go to /user/profile or click the link in the user menu.
• Admin interface for viewing and rejecting contributions, including a reason why it was rejected.
• Users can view, but not edit, their own contributions, if any, by going to /library/my/contributions (same route as before) or clicking the link in the user menu.
• Ability to accept new contributions is controlled by a config switch, allowContributions (boolean).
• The route /library/contribute is now operable, but largely incomplete. For now, I recommend setting the setting mentioned above to false, and advising admins to not click "Create Release" in the admin interface contribution page.

[NattyNarwhal]

Code wise this looks good so far, and I'll give it a try locally, but some thoughts:

• As mentioned on IRC, I need to flesh out the design for the contributions system to make it simpler than the previous system in terms of maintainability. Avoid things like crazy FTP setups. This looks fine, I'll just provide some design documentation to make the original vision clear, since it's been stuck in my head for years now.
• User profile code looks fine, but I'm not sure if public user profiles are appropriate for the CMS itself, since generally users don't care about other users, except in a forum context. This could change if we ever move forums and such internally into the CMS though.

[nitinseshadri]

I'm not sure if public user profiles are appropriate for the CMS itself, since generally users don't care about other users, except in a forum context.

Yeah, the idea is that these will become the profile pages for the forum at some point. Vanilla allows you to set custom profile URLs, but it would require some changes to the SSO code as detailed here: https://open.vanillaforums.com/discussion/28209/change-the-url-of-user-profile
EDIT: Look at the very last post in the thread for full instructions.

[nitinseshadri]

@NattyNarwhal Any updates on this?