- removed imported source from slick-migration-api

Deleted imported source code from https://github.com/nafg/slick-migration-api project.
Add dependsOn github.com/nafg/slick-migration-api github project instead of in the build.sbt.
- implements build limit feature

Implements the deleteion of old builds except the configured build limit count of
the youngest.

See https://trello.com/c/8VocyKNW