creation of books medium relevance component
Revert "Merge pull request #4382 from guardian/revert-pull-request-4381"

This reverts commit d9227ca2dfa630e5cf6fe703c5488809595d2e38, reversing
changes made to 071544d6f5bf607f0195ddf277d726533e6be148.
URLencode SVG
adding text fallback for search forms
Book feeds can have explicit books shortlisted.

First pass at this feature.
Made param less explicit.

Makes it easier to put in other places.
spacefinder
mobile ad placement
spacefinder tests
Set Component Max Age
renaming splacefinder
removing excess padding for travel component
Merge branch 'master' into commercial-comp-bugs
Cache Book Offers
Cache Job Offers
Cache Masterclasses
Cache Money Offers
Cache Soulmates
Merge branch 'master' into kc-cache
add survey message on top of any page
- show message only after 3 visits
- don't show message in case it was closed