Create a metadata postprocessor for setting container name in metadata

There are multiple deployers currently which first check whether the container name is set in metadata. If it's not available then the deployer generate a container name, using the deployment unit. This code is duplicated across multiple deployers currently.

Introduce a post processor which sets the container name in the metadata if it's not already set. The other deployers can just get hold of the container name from metadata henceforth.