Update from one i-doit version to another

[bheisig]

Expected behavior

It should be possible to update i-doit by pulling a new image. There must be a logic to check whether DB backend needs an update. If check is positive then update should be performed in background before container is ready for connections.

Additionally, we should work with version independent tags, for example open-apache-latest.

Actual behavior

Update logic hasn't been implemented yet.

Steps to reproduce the behavior

1. Run image with older version
2. Pull new image
3. Restart container

Environment

Any