Add new "remove_event" permission

This permission may be used to disallow event removal, without
disallowing the other event actions (Mute, Share, etc). Since
this is a new permission, we fall back to "admin_event" if
"remove_event" is not False.
Merge pull request #1251 from jaysoffian/remove_event_perm

Add new "remove_event" permission
Various improvements to logging/imports
lol
Allow superuser status to be set on Admin page
Merge pull request #1253 from jaysoffian/admin_superuser

Allow superuser status to be set on Admin page
Implement managed users feature

A managed user is authenticated externally to Sentry, for example
via basic auth by the web server. Such users should not be allowed
to change their username or password from within Sentry.

A new configuration setting, SENTRY_MANAGED_USER_FIELDS, can be
used to further prevent a managed user from changing their name
or email address.
Hide account identities tab if there are no auth providers

If there's no configured auth providers, there's not much reason
to show this tab.
Merge pull request #1256 from jaysoffian/hide_identities_tab

Hide account identities tab if there are no auth providers
Change tag conditions to base case insensitive
Remove dead "get_version" code

This code dates back to 2aa95f5662 (Display appropriate 'best guess'
version for executing application, 2011-01-03) and is AFAICT completely
unused since at least 75ef8739fe (Move validation logic into coreapi
and remove support for legacy data, 2012-04-08).
Merge pull request #1259 from jaysoffian/remove_unused_get_version

Remove dead "get_version" code
Remove remaining unused versions code

All of this relies on Group.data["version"] which nothing appears
to populate anymore, and is being replaced in the future by a more
robust "releases" concept anyway.
Merge pull request #1260 from jaysoffian/remove_unused_get_version

Remove remaining unused versions code
Update static
Implement is_regression plugin check

Add a plugin call, "is_regression", called on new events when
the group's status is STATUS_RESOLVED. The call may return
True if this event is a regression, False if it is not, None
to defer to other plugins.

For example, a plugin may wish to examine a tag's values on a
group and only consider the event a regression if it is
contributing a new tag value.
Merge pull request #1261 from jaysoffian/plugin_regression_check

Implement is_regression plugin check
Merge pull request #1255 from jaysoffian/managed_user

Implement managed users feature
Use compact separators when json encoding
Fix broken json tests