Workspace window rules

[YaLTeR]

I'm thinking, just have the window rule blocks inside a workspace "name" { block. (And, as a separate issue, a layout {} block too?)

The alternative is match workspace="name", but this will cycle with open-on-workspace, which the solution above avoids.

Example use: having a "sensitive" workspace where all windows are blocked out from screencast: #1009

[plum]

To me the idea seems intuitive when writing out the window rules, and would make subsequent reviews of a config file straightforward.