Cosmetic, actions: renamed "Lower Floor/Ceiling by 8 mp" to "Lower...

Cosmetic, actions: renamed "Lower Floor/Ceiling by 8 mp" to "Lower Floor/Ceiling/Thing by 8 mp", "Raise Floor/Ceiling by 8 mp" to "Raise Floor/Ceiling/Thing by 8 mp", "Lower Floor/Ceiling by 1 mp" to "Lower Floor/Ceiling/Thing by 1 mp", "Raise Floor/Ceiling by 1 mp" to "Raise Floor/Ceiling/Thing by 1 mp", "Lower Floor/Ceiling to adjacent sector" to "Lower Floor/Ceiling/Thing to adjacent Sector/Thing", "Raise Floor/Ceiling to adjacent sector" to "Raise Floor/Ceiling/Thing to adjacent Sector/Thing".
Updated, Visual mode, "Raise Floor/Ceiling/Thing to adjacent Sector/Thing" / "Lower Floor/Ceiling/Thing to adjacent Sector/Thing" actions: sectors across targeted sectors are now taken into account when determining target height.
Updated, Visual mode, "Raise Floor/Ceiling/Thing to adjacent Sector/Thing" / "Lower Floor/Ceiling/Thing to adjacent Sector/Thing" actions: the actions can now stack things on top of other things when their bounding boxes intersect. 
Internal: cosmetic changes to shader update logic.
Internal: thing bounding box is now used when adding a thing to VisualBlockMap.