Image resizer

Lets get this merged. 

@daithiocrualaoich spent a few days on this a couple of months ago.

 - DONE Scan for Play 2.1 etc. compatibility
 - DONE Corresponding configuration in the platform project, dashboard graphs - see guardian/platform/pull/75
 - DONE (waiting on websys) A host name equivalent to _static.guim.co.uk_ via websys
 - DONE (we'll use prod, unless you are doing dev work) Plan for _localhost_ - feels a bit slow.
 - DONE (max-age=86400) Needs cache-control headers on the image outbound response header
 - DONE Needs a switch between this and origin - see #669 
 - DONE Test with low traffic on frontend to benchmark performance in PROD - see #669

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 - Benchmark on AWS server