New module to import and process benchmark output

This is the beginning of a module to import and process benchmark
outputs.  The module currently supports importing of a bench.out and
validating it against a schema file.  In future this could grow a set
of routines that benchmark consumers may find useful to build their
own analysis tools.  I have altered validate_bench to use this module
too.

	* benchtests/scripts/import_bench.py: New file.
	* benchtests/scripts/validate_benchout.py: Import import_bench
	instead of jsonschema.
	(validate_bench): Remove function.
	(main): Use import_bench.