Fix bad docstrings

Sphinx autosummary uses the top line of the module's docstring to populate the TOC, among other parts of the docs. A blank line at the top of the docstring results in a blank space in those areas of the documentation.

Also, I removed a shebang line from the top of salt/states/zcbuildout.py, because it is not required in Salt code, and added docstrings to a few modules that lacked them.