The Read-Only Confusion

### Describe the issue

n a glossary, the user is supposed to set the 'read-only' flag on a string to mark it as 'untranslatable'.
At the same time, the flag is also used to indicate whether a string can be edited (e.g. to disable editing of the source language strings).

There are two completely different things and should not be mixed up. 'untranslatable' indicates a policy to adhere to when translating and the other use is simply about controlling user input in the editor.

This creates the nonsensical situation that when you are editing the source language (screenshot), it is impossible to see whether a string is marked as 'untranslatable', because the UI display doesn't change when marking or unmarking a string as 'untranslatable': It always shows the read-only flag and the "String is readonly" text.