add minimum_renku_version on project metadata and raise a warning

[Panaetius]

Sometimes we have changes that break forward compatibility of older versions without changing the metadata version. In these cases, a user doesn't need to run a migration but they do have to update their renku version to be compatible.

We should add a minimum_renku_version on project metadata that we can set in code (and update if a write command is run with a newer renku version). Probably a CommandBuilder to set this makes sense.

Then we should check this when running any renku command and warn the user if their renku version is lower than project.minimum_renku_version