CORE-1618 Support defining createProcedure body in an external file

Refactored new code and fixed failing tests
Fixed dropProcedure example and added saved_state test output
Split out dataDir logic from MissingDataChangeGenerator to a more generic mechanism
Merge branch 'master' into LB-3.1-testing
[maven-release-plugin] prepare release liquibase-parent-3.1.1
[maven-release-plugin] prepare for next development iteration