Provide Util.setSettingsDirectory for git and cvs

Some providers like clearcase, vss and svn (i.e. see SvnUtil) have the ability to set the SettingsDirectory. It would be a huge improvement to add this to the GitUtil and CvsUtil as well, so I can use them in my tests without breaking my own scm-settings files. Other providers don't seem to have a specific settingsfile, so there's of course no need to add them there.