Move to astropy-affiliate package

Manually added files and directory structures necessary to be an astropy
affiliate package (include setup and testing frameworks).
Setup sphinx documentation.

This commit adds/sets up sphinx documentation in `docs/`. I still need
to implement the documentation itself and update docstrings to conform
to the numpy format.
Add module api reference doc pages

- Add imagelog module api reference
- Add astromatic api reference
- Add twomass api reference
- Add dbtools of API docs
Add intro rst document
Remove old sphinx directory
Add ImageLog usage doc page