Improved comments in the config file.   See SF Support Requests #423

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2795 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7
Replicated changes from Rev 2793 and 2794 to the systemdefaults file and also extended to 'db_ext' settings

git-svn-id: http://svn.code.sf.net/p/mrbs/code/mrbs/trunk@2796 25f7e783-145e-4f2d-a9f8-dd7182bfe9c7