Documentation Overhaul
- Added documentation hierarchy
- Added options for Bash vs Python for API & Upstream Connectors
- Added Introduction section (Overview, Key Concepts, Getting Started)
- Redid connectors section
- Installation is now broken up (needs further work)
* fran-unstructured/Add unstructured API documentation
* fran-unstructured/add api docs to index.rst
* fran-unstructured/add api docs with changes requested