[WIP] Very plain doc conversion for Dash

A very simple script to generate a Kapeli Dash docset.

TODO:

 * [ ] get some feedback
 * [ ] document+automate submission to https://github.com/Kapeli/Dash-User-Contributions
 * [ ] make SQL output in gendocs optional and/or just always generate everything (html+dash) from a makefile-or-something

(Note that there would be nothing wrong with merging it now, imo, except gendocs.rb now writes surprise SQL to stdout :angel: )