Add CLI regression testing

Adds high-level regression testing by installing datasets using the CLI and comparing the results
to the current results based on md5 checksums.

Currently tests only engines that directly produce files (csv and sqlite) and includes tests of
three datasets that cover the range of complexity for simple text scripts (AvianBodySize,
DelMoral2010, and MoM2003).

If there are better ways to do this I'm certainly open to reworking things. I'm viewing this as the
highest level safety net to allow us to do any necessary refactoring to make it easier to write more
specific tests.