Agenda for TPAC

Hi,

Assuming we're going to be discussing Level 2 at TPAC, I've created a straw
man agenda for us.

There's a bunch of things we've punted from Level 1 which make good
candidates for a discussion, and I've added those to the list. I fully
expect this to all be changed :)

https://www.w3.org/wiki/WebDriver/2017-TPAC-F2F

Simon