Last Search Fix

DSC-950

Fixed the problem where the "Back to search results" would take the user to a search they didn't perform.

* Renamed the URIMemoryService to LastSearchMemory
* Removed explicit spring XML config in favour of annotations
* Changed the behaviour to store the last search against the user id instead of a common string. This was causing all the problems as the Service is singleton.
* Changed the UI display to make button more discreet by moving to the Work / Copy navbar and making the colour light blue.