provide git:// transport to keep submodule compatibility

ditto

assigned to @dcobas

The git daemon has been installed in ohwr-gitlab.cern.ch. At the moment, the following assumptions are valid:

• it serves all repositories (--export-all option)
• in standard port 9418
• local to CERN only
• this required modification of SELinux types of the base path

Nedds to be done:

• pierce firewall
• open up only the repositories that might be needed, selectively