PSD import via psd_sdk

[LunaTheFoxgirl]

I am working on and off on an entirely D solution that's more cross platform, but the PSD format is the worst abomination mankind has created. So for the time being we'll be using the psd_sdk library to parse PSDs, psd_sdk is currently only available on windows, we'll be keeping the temporary binding in-source-tree. And use compile time shenannigans with a version tag called ENABLE_PSD to turn on the PSD binding.

[LunaTheFoxgirl]

I'll be re-attempting to do it from D by using psd_sdk as reference since its implementation seems easier to understand than some of the ultra messy C code there's around

[LunaTheFoxgirl]

This has been implemented for a while now