Major refactor of the docs, phase 1

Move to use the astropy affiliated package template for the docs,
started on a proper api doc using astropy and fixed some docstrings
add back in other doc pages
one warning in guide and other tweaks
re-add examples
add auto templates
more database guide
refactor guide
add new dirs
fix intersphinx
remove mock
DocSprint: citation up to date - resolves #693
DocSprint: citation - lines break added for easier track
update doc requirements.txt
remove database guide (temp)
more database murder
remove reference to database
Add titles to all sections of the api reference
remove ref to database
DocSprint: VSO module restructuration.  Fixes #686
fixes to vso