Add possibility to use tpatlas ( Texture Packer file) or atlas

[defoldino]

Currently only .atlas can be used, this means to not be able to use the minimum size possible, packaging images that will be use by Spine in .atlas and others in tpatlas.
Being able to use .tpatlas, atlas format from Teture Packer, will achieve this.

https://defold.com/extension-texturepacker/
https://github.com/defold/extension-texturepacker