Fixed a bug where zooming could position the camera off the pixel grid
and cause interpolation of the texture.
Modified the camera movement routine of the renderer to be more
resilient against drifting off the pixel grid and thus causing unwanted
interpolation of the texture.
Fixed another bug related to interpolation artifacts, this time due to
resizing of the window. The viewport and projection matrices are now
based on whole numbers that should always result in transformations
adhering to the pixel grid.
Fixed bug where camera movement would receive a constant drift when
window size was an uneven number of pixels.