-minor fix, gets back ~5% solve time
-used groupby() in two places to avoid redundant version-in-range tests
-added optimised containment test in VersionRange for already-sorted version lists
-added version unittests back in
-added test for new optimised containment tests
-various improvements to intersection tests etc in version module
-added more version tests
-fixed bug in resources, not all caches being cleared in clear_caches()
-all tests passing once more
-various minor updates to solver, only a small effect on performance
-removed thread-related code from version parser, no longer needed with pyparsing gone
-removed unnecessary use of config module in solver.py
-fixed bug introduced in gui on context save
-fixed bug where rez-search ignored --no-local option
-fixed release bugs:
 * local packages were not being ignored;
 * broken previous build rxt file no longer used
-updated 'rez-status' tool so it's a simple general tool easier for artists to use
-removed 'Open Active context/suite' option from rez-gui. Too confusing - when
   gui launched as wrapper, active context/suite is not as expected.