NOJIRA Added option to set search engine plugin settings via constant

This is useful if you have a multi-instance setup where all instances
use the same set of config files, i.e. where you have no other way to
set these settings on a instance-specific basis. This way you can set
these settings in setup.php depending on the hostname of the current
request.
Merge branch 'master-fix' into develop

Conflicts:
	app/lib/core/Plugins/SearchEngine/Solr.php