Version 0.4.1

This release extends the functionality of the "builders" framework, which includes the command-line tool "mgbuild". It also attempts to make the builders easier to use and better-documented. Some of these changes are not backwards compatible, both in the mgbuild command-line options, and some minor changes in the builders API. It is believed that all the users of the builders are the internal MP team and close collaborators, so now is a good time to make these kinds of changes.

Other internal changes include modules to read entire directories of DB configuration files into a single object. This will be the basis for upgrading the "sandbox" implementation in the MP website.