MB-17176: Docroot in pluggable-ui-*.json now relative
MB-17176: Docroot in pluggable-ui-*.json now relative

To fix problem with installing couchbase in different locations
on different platforms. The docroot given is now a relative path.
At runtime $install/lib is prefixed to the given path.

Change-Id: Iefcb77a6294c60a9b47a6c3ce36b704f5801b335
Reviewed-on: http://review.couchbase.org/58240
Tested-by: Anders Nygren <4f8bff4ce020de40cfee5db6ca7fd51acc06e5c4@couchbase.com>
Reviewed-by: Dave Finlay <7b10a9ed9f70e64c30b07607a671ae61c33f14c8@couchbase.com>

ceejatec/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server