Restructure the OrcaWare Subversion repository to have the 'more'

standard Subversion repository layout where each project has
underneath it the branches, tags and trunk directories, instead of
having a top level branches, tags and trunk directory with each
project underneath.

* orca:
  New directory.

* orca/branches:
  Renamed from branches/orca.

* orca/tags:
  Renamed from tags/orca.

* orca/trunk:
  Renamed from trunk/orca.

* orca/trunk/CHANGES,
* orca/trunk/README.DEVELOPERS:
  In all URLs referring to the OrcaWare Subversion repository, change
    http://www.orcaware.com/svn/repos/trunk/orca/
  to
    http://www.orcaware.com/svn/repos/orca/trunk/
  and
    http://www.orcaware.com/svn/repos/tags/orca/
  to
    http://www.orcaware.com/svn/repos/orca/tags/