Create tapicero.md

Copy tapiceros readme into leap_doc.
Add tapicero to menu
Add database setup section to overview

Explaining setup of 'normal' and per-user databases. link to tapicero, point out where the design docs come from and where they go.
Emphazise usage within leap platform for tapicero

Sorting the sections so the usage scenarios for the platform come first.
Merge pull request #7 from azul/tapicero

Initial Tapicero documentation