DOC: add GEE to docs, rough addition/edit of docstrings
REF/DOC GMM update docstrings, rename start -> start_params in fit signature
DOC: sphinx/rst warnings, fix var_plots closes #1250
DOC gee doc typos, improvements, gmm remove stray print [ci skip]
Merge pull request #1264 from josef-pkt/doc_work

Doc work GEE, GMM, sphinx warnings