Adopt Rapid's performance improvements

[matkoniecz]

Reportedly Rapid is noticeably more performant than iD - can this performance improvements be ported back to iD?

[bhousel]

Rapid is a nearly complete rewrite of iD. It's not just a few performance tricks that can be dropped into the legacy iD code.

[jjiglesiasg]

Some poweruser features could be handy to have in ID