EMI: Implement projection shadows.
EMI: Calculate actor bounding box correctly.

This is necessary for Actor::shouldDrawShadow to behave correctly, but
could also affect collision detection.
EMI: Enable shadow sprites.
GRIM/EMI: Make Light and SetShadow structs instead of classes.
GRIM/EMI: Use Doxygen style for the comments.
EMI: Implement projection shadows for OpenGLS renderer.
GRIM: Initialize _shadows to null.
EMI: Do not print a warning if Actor::getBboxInfo is called for an actor that doesn't have a model.
Merge pull request #956 from Akz-/emi-shadows-rebase

EMI: Implement shadows for OpenGL and TinyGL renderers