Add a search function to the "Datafiles" tab of the OpenMW launcher

Old titel of the issue was:

Add a "Sort Alphabetically" button to the "Datafiles" tab of the OpenMW launcher

it seems that it is not possibel to strikethrought text in the title of an issue (sorry I didn't knew that, I'm new here).

That would help mod testers like me saves alot of time. Of course only if it is not to hard to develop and theres time and space for that. ;)