Item11267: Make the git-svn connection optional

git-svn-id: http://svn.foswiki.org/trunk@17902 0b4bb1d4-4e5a-0410-9cc4-b2b747904278
Item12952: In-progress changes to split configure between the core and contrib. Current state has all the meat of configure in the core, and the non-working bits left in the contrib.

git-svn-id: http://svn.foswiki.org/trunk@17903 0b4bb1d4-4e5a-0410-9cc4-b2b747904278