Initial support for common JUnit DB

[ZakarFin]

Creates a membased DB datasource for unit testing if a class from the shared-test-resources is present in the classpath. Checking things with reflection API so we don't need to add the test-module to dependencies but can detect test env if the class file is available.

Separated from #271 waiting for further development for this to be actually usable.

[ZakarFin]

More recent testing: https://github.com/oskariorg/oskari-server/compare/develop...ZakarFin:testdb?expand=1
Still struggling with the cyclic dependency ref. Probably needs refactoring of current modules or detaching tests to another module to make it work properly. Note! Upgrading Flyway means dropping postgres 9 support: https://flywaydb.org/documentation/database/postgresql