perf-model: import cleanups
	eliminate some duplicate unit definitions
	remove some unnecessary imports
	pep8

Signed-off-by: Mark Kampe <mark.kampe@gmail.com>
performance model: create sample subclass of SimFS
	It is intended that it should be possible to create
	non-open-source sub-classes of SimFS.FS, so I created
	a sample (zfs.py) of such a sub-class.

Signed-off-by: Mark Kampe <mark.kampe@gmail.com>
performance model: factored out standard report generator
	wrote a standard columnar report generator
	modified test modules to use it for reporting
	designated test modules as applications under LGPL

Signed-off-by: Mark Kampe <mark.kampe@gmail.com>