Re #8909. Detached MdiSubWindow from ApplicationWindow
Merge branch 'master' into feature/8909_tiled_graph_displays

Conflicts:
	Code/Mantid/MantidPlot/src/MdiSubWindow.cpp
	Code/Mantid/MantidPlot/src/MdiSubWindow.h
Re #8909
Re #8909. Added TiledWindow window class
Re #8909. Use EmptyTile widgets to fill in empty spaces.
Re #8909. Added selection of tiles.
Re #8909. More visible border for selected tiles.
Re #8909. Added range selection with a mouse.
Re #8909. Selection, deselection and removing ranges of widgets.
Re #8909. Implemented window reshaping.
Re #8909. Added a menu for tiled windows.
Re #8909. Implemented dragging and dropping of floating windows
Re #8909. Added drag and drop of floating graphs to TiledWindow.
Re #8909. Removing widgets from TiledWindow with drag and drop.
Re #8909. Dragging graphs from docked windows, and to floating tiled
windows.
Re #8909. Marking insertion position between tiles.
Merge branch 'master' into feature/8909_tiled_graph_displays

Conflicts:
	Code/Mantid/MantidPlot/src/ApplicationWindow.cpp
Re #8909
Merge branch 'master' into feature/8909_tiled_graph_displays

Conflicts:
	Code/Mantid/MantidPlot/CMakeLists.txt
Re #8909.
Re #8909. Widgets can be inserted into TiledWindows.
Re #8909. Fixes to TiledWindow reshaping and moving widgets.

Updated python interface. Added new tests.
Re #8909. Fixed compiler warnings.