* save permissions, relationships and collections in catalog with 'is_system_defined'
* Use common stanzas in the .cabal file
* Refactor migration code into lib instead of exe
* Add new server test suite that exercises migrations
* Make graphql-engine clean succeed even if the schema does not exist
* Bump node-sass to version ^4.12.0
This avoids sass/node-sass#2632, which causes compilation failures on
Node v12.x.
* Do most of the work in /pg_dump in Haskell instead of shell
The shell version caused problems on non-Linux systems since it relied
on the non-POSIX -i option for sed, which works slightly differently on
BSD and macOS.
