sdss/marvin: Marvin Beta 2.5.2

This release is primarily for code health. It makes the following changes: Removes all extern submodules. Converts all submodules to pypi releases Adds new dependencies for marvin-brain, marvin-wtforms-alchemy, marvin-sqlalchemy-boolean-search, sdss-tree, and sdss-access Simplifies setup.py and dependencies. Moves requirements files into setup.cfg. Switches to sdsstools for internal logging and config management Moves tests out of python package directory to top leve