Keystone V2 is deprecated in favour of V3. This adds the necessary
connection parameters for establishing a V3 connection. Connections
to V2 endpoints are still possible and the configuration should
remain compatible.
This also introduces a SWIFT_REGION variable for multi-region
OpenStack environments and a SWIFT_CACHE_TTL that controls how long
tokens and other meta-data is cached for. Caching tokens avoids
rate-limiting errors that would result in media uploads becoming
unavailable during high load or when using tasks like
media:remove_remote. fog-openstack only supports token caching for
V3 endpoints, so a recommendation for using V3 was added.
If an :original gets converted into another format, it would get saved as
original_filename *anyway*, so generating the extension is pointless and
yields bad results for when you change the style definition later. This way,
old gifs will still have correct URLs
for avatars/headers, resize avatars down to 120x120 instead of 300x300. Set cache headers on S3 stuff, also
make it private (aka only accessible via expiring links to prevent hotlinking)
