Module Docs Should Have Default Key

AFAIK the module documentation is generated by looping over a `ModuleManager` instance. This means the routine for creating the documentation should also be able to update the documentation with what the default key is for the module, e.g., in ChemCache it would be great if the documentation [page](https://nwchemex.github.io/ChemCache/module_api/NWX_Molecules.html) for the `NWXMolecule` module said the key was `"NWX Molecules"`.