Ability to set state to 'empty' on Bulk Edit

[emmapeel2]

I need an easy way to remove erroneous translations while mantaining our project.

It would be great to be able to set state to Empty for example in https://hosted.weblate.org/projects/tor/tor-browser/tb-android/#bulk-edit

I think this power should be only for mantainers of the translations, not needed for translators or reviewers.

In my case, my translation memory is contaminated with source strings, and I want to make empty all the strings that have check:same.

[nijel]

Tracked as #11887