* [API] Implement a toolbar registry and a plugin to allow providing a toolbar for a selected object.
* Modify the mct-toolbar directive to get the toolbar structure from a provider based on selection.
* Implements the layout toolbar in the layout bundle
WTD-1048
Originally did a lot of this work in warp1048 by mistake
This commit pulls in all /platform-only changes from that branch
Mods are mostly related to WTD-1046 specifically, but also touch toolbar and buttons
Avoid rebuilding the toolbar in Edit mode whenever
any change occurs to avoid losing the binding to the
current selection state; needed for color picker to
work properly for WTD-881.
