- Fixed config file parsing for null groups when a group

- Fixed config file parsing for null groups when a group
  name was the same as an assignment immediately following
  it.
- Added support for undefined groups at the time of assignment.
  If a given group does not exist, an empty group will be
  created and a warning will be issued.
- Make method cleanupString() in SCST::SCST private.
- Minor updates.

git-svn-id: https://scst.svn.sourceforge.net/svnroot/scst/trunk@219 d57e44dd-8a1f-0410-8b47-8ef2f437770f