Feature request: Backup of module files when using --module-only --force

[damianam]

Background: We might need to add properties to modules after SW has been installed already. I'd like to have a backup of the old module to compare contents with the new and make sure that what is there is consistent, since it is not guaranteed that the module generated with --module-only is exactly the same as when going through the whole process.

There are workarounds like using --installpath-modules, but this is error prone, and once a file is overwritten it is gone.

[damianam]

See #2134

[boegel]

let's follow-up on this in #2134