poc(components): drawer portal interface

[gribnoysup]

An initial pass for the drawer portal interface that we need to be able to declaratively define independent sections of the drawer across various parts of compass application (think separate plugins adding their own sections to the drawer without drawer component needing to manage the state of those). I'm opening this as a draft just to show the interface, there are some issues with the leafygreen drawer that you can see if you run this branch locally:

• The way the grid styles are defined just completely break our layout (I don't think they are doing grids right, but I need more time to investigate)
• Also it seems that having Drawer render over anything that contains vitual grids completely breaks them, another thing we will need to investigate