Changed several filename attributes of TestConfiguration to be constant global variables
Changed documentation to google python standards.
Added methods to TestData to produce paths for gold or output directories.
Added additional helper methods to TestData to eliminate overuse of make_path
Replaced usage of make_path with attributes and methods in TestData
Created DiffResults class to store TskDBDiff results in TestData.
Merge pull request #233 from jawallace/master

Regression Script Refactoring