Invalid xml character cleaner
Merge branch 'master' of github.com:guardian/frontend into foresee-assets
Clean invalid XML characters from CAPI fields

When producing RSS a few of the CAPI contain invalid XML characters, so we need to clean them.

This is currently the sole cause of 500 errors on NGW RSS feeds.

From testing a few hundred feeds the problem (?) seems localised to only a few fields, so I've only fixed them.
Test to replace xml control characters
Merge pull request #3677 from guardian/fix-xml-control-chars

Fix xml control chars