[INTERNAL|API] added VCSProviderFactory core INTF and Eclipse IMPL

Change-Id: Ie45106224014bafe738494f53b794e500381f4e2
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1740
Tested-by: Saros-Core QA
Tested-by: Saros-Eclipse QA
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>