implement preloading for assets

[michaelthatsit]

Model and asset loading can be slow. not Insanely slow but slow enough to not appear immediately. This can result in a failure to be immediately processed by other systems at launch.

proposed solution is to parse the document for all tags that are loading a model, load those models, and then initialize the rest of the app. Models loaded more than once can utilize instance meshing by default to avoid loading them more than once.