Humble backport diff_drive tf_prefix | change tf separation from / to _

[delihus]

Backporting a feature with tf parameters for diff_drive and changing the separator from / to _.

[christophfroehlich]

This is a duplicate of #726, which got stuck because of a merge conflict. @bmagyar could you have a look there please?

[delihus]

This is a duplicate of #726, which got stuck because of a merge conflict. @bmagyar could you have a look there please?

Ehhh... yeah...
I didn't notice. Overall what about changing the / with the _. It is not common to use the / in tfs.

[codecov]

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