ZENGINE: Rename variables and add comments to clarify the math behind panorama warping
GRAPHICS: Create copyRectToSurface member function
ZENGINE: Apply panorama/tilt warping after all images have been rendered to a backbuffer

This makes wrapped warping much easier as well as allowing changeLocation offsets to
work properly
ZENGINE: Convert Surface::pixels to Surface::getBasePtr(0, 0)