Template dialogue displays more than just template files

Viewing the above screenshot from my latest build shows the template dialogue listing the files in MuseScore's default Templates directory (that will vary according to your system).

It can be seen that the dialogue currently lists everything in the directory, albeit with files which aren't templates greyed out.

Only the template files should be shown, and we need a way to suppress the display of the hundreds of localised instrument files in this dialogue.

I have been looking at this code, and if I can work out how this is done I am happy to undertake this - any clues or pointers would be welcome :) But I'm not assigning myself until I'm sure I can achieve this.

Build based on MuseScore 2 release 62803b8
OS Windows 8 Pro