Add MiMiCPy docs
- Added changes to Installation section, included instructions for MiMiCPy
- Added MiMiCPy section, detailing:
- an overview of MiMiCPy
- a page on PrepQM (with explanations on the usage, options, selection keywords, VMD/PyMOL plugins)
- a page on other sub-commands, with an explanation and description of options for each