Provide additional command descripton when initiating "/OTG Export" in game

i.e: Export [centre_block] [-a include_air] [-t include_tile_entities] [-o override] [-bo4] [-b use branches]

(as shown in previous OTG version on attached image)

Needs another pass

Is this one finished?

Has already been handled, just we forgot to close.

Up to @authvin if he'd like to pick this up for 0.0.1 or 0.1.0.

I'll do this when the command is finalized, it's been in a state of flux as to which arguments come where. I can add a simple one for the next build though