texture: Rework error enum

texture: Rework error enum

1. Change INSUFFICIENT_MEMORY to TOO_LARGE
   GTK crashes on insufficient memory, we don't emit GErrors.

2. Split UNSUPPORTED into UNSUPPORTED_CONTENT and UNSUPPORTED_FORMAT
   So we know if you need to find an RPM with a loader or curse and
   the weird file.

3. Translate error messages, they are meant for end users.