This reverts merge request !802

So we don't flood our postgres logs with errors. Should also make things
slightly faster.

```
# Only return statuses that have been pinned
GET /api/statuses/user_timeline.json?pinned=true

# Pin
POST /api/statuses/pin/:id

# Unpin
POST /api/statuses/unpin/:id
```

Also rename seconds_retained to seconds_valid since that's how it is
now. Put it down from 180 to 20 seconds. The answer data is now
stored in an encrypted text transfered to the client and back, so no
ETS is needed

Introduced User.register/1 to encapsulate User record creation and post-registration actions.

[#114] Account confirmation email, registration as unconfirmed (config-based), auth prevention for unconfirmed.

[#114] Refactored `password_reset` (moved to TwitterAPI). Added homepage links to password reset result pages.

Refactoring.

to `update_media` action. Added controller tests for `upload` and `update_media` actions.
Refactoring.

Related to #85

Everything should now be configured at runtime, with the exception of
the `Pleroma.HTML` scrubbers (the scrubbers used can be
changed at runtime, but their configuration is compile-time) because
it's building a module with a macro.

if using local media, the mediaproxy will not replace the URL anyway.