Add Texture Optimization about pman

[rdb]

For the record, you can tell Panda's model-cache to cache textures as .txo automatically using model-cache-textures true. Also, when converting models using egg2bam, you can use the -txo flag to automatically convert textures referenced by the .egg file to .txo.

[Moguri]

Those are good to know, thanks!

The current why pman handles conversion, it would be nice to separate texture compression from model conversion. However, maybe it makes sense to change up how pman does model conversion so it can take more advantage of Panda features.