Request: Execute --cleanup only for a certain language

[malua]

Hey,

This is a complementary ticket to my other one #138.

It would be nice if it is possible to execute --cleanup only for certain languages when running phrase push --cleanup --wait.

Otherwise all the untranslated keys in the target languages will be deleted.

All the best,
Lukas

[forelabs]

As you said, this is complementary for the other request.
I do believe when we introduce the option on language level, this means it won't be applied to languages where it is not defined so this request would be resolved automatcially.