Add support for window docking in the property sheet code

This checkin migrates more of the WindowBuilder code into the property
sheet library; in particular, it adds the window docking code for use
with the property sheet in ADT. There are also some modifications to
the code to support ADT use cases, documented in the updated README.

Change-Id: I38e0e2137fdcc179aa6f8927d201ff002c831617
20 files changed
tree: f456b9a3b7e64bee9a8f9980f58c641aa6dc3a7e
  1. propertysheet/