Add VRF Controller
Factor RefrigerationSystemGridView into base class

Create GridLayoutItem which is a QGraphics item to layout other
QGrahpicsItems in a grid view.  It works with OSListController.
Extracted the common functionality out of RefrigerationSystemGridView
and moved it to a "shared_gui_components" class.  This will be reused
for VRF grid view.
Develop VRF Views
Add support to drag and drop VRF Systems
Fix deficiencies in clone, remove, and children
Show name of VRF system in header
Add (incomplete) VRF detail view
Make VRF system inspectable
Factor out new class OSDropZoneItem

This is the same as OSDropZone but made to work with QGraphicsScene
instead of QWidget.  Much of the custom painted interface in HVAC uses
QGraphicsScene.  OSDropZoneItem was factored out of
RefrigerationSystemDropZone so that it can be reused in VRF interface.
Add feature to drop terminals on VRF system
Add VRF terminal to library

Show VRF terminal category in library.
Fix issue where terminal could be added twice on drop to VRF system.
Add VRF terminal image and remove button
Use base class for VRFSystemDropZone
Add remove button for zone and VRF terminal
Make VRF terminals inspectable
Make cosmetic improvements
Fix error VRF terminal clone

When cloning ZoneHVACTerminalUnitVariableRefrigerantFlow into the same
model, node connections would be left pointing to the old attached
ThermalZone.  This is wrong and a fix has been made.  This should be
considered for the base class ZoneHVACComponent.
Add message boxes to explain VRF interface
Add details to VRF summary view
Add curves as children of VRF coils