Add flyway migration Dockerfile
Add flyway migration Dockerfile

This Dockerfile extends the base flyway image to include
the database patches in `db/patches`.

We need this Dockerfile if we want to have a completely
sourceless environment for the live server.

hemberger/smr,hemberger/smr,hemberger/smr,smrealms/smr,smrealms/smr,smrealms/smr,hemberger/smr