Added support for non-branching files (Streams only).
If a *.nobranch file exists in the config directory when
processing updates, the files specified in the *.nobranch
are not added to version control unless the stream type
is 'mainline.'
The *.nobranchg file (e.g. FGS.nobranch) contains a list of
non-branchign files, one per line, with a path relative to
the root of a workspace).