add sort indicators to generators pages

when a header is clicked, an icon will show which sort it is doing. by default it doesnt show any sort going on. 
[preview](https://www.evernote.com/shard/s18/sh/b6943fa1-c2a3-47b3-9060-12aa47e01993/d1b1d6cf146731ff7ba0ba29c764d98d)