Added recipe search by skill, or only skill used. Results are nicely sorted!

Crash fixed, thanks @BevapDin and @macrosblackd!

This PR allows you to search recipes by skill, much like you would my tool or component. It skips over recipes without skills; that's simpler, and I expect people to use this search function to look and see what's new. Perhaps I will update it to list recipes in order of skill level...