Added documentation and test coverage.

compare_perf_test.py is now covered with unit tests and public methods are documented in the implementation.

Minor refactoring  to better conform to Python conventions:
* classes declared in new style
* proper private method prefix of single underscore
* replacing map with list comprehension where it was clearer

Unit test are executed as part of validation-test.

.gitignore was modified to ignore .coverage and htmlcov artifacts generated by the coverage.py package

.gitignore

@@ -51,3 +51,5 @@ compile_commands.json
 8
 4
 SortedCFDatabase.def
+htmlcov
+.coverage