Added MIP map so image scales down nicer

[rj200]

Will fix aliasing that @Tom | Dermotius reported in Discord.

[CeeJayDK]

Code looks sane so far. I'll test it and polish it sometime this week.

[ghost]

MipLevels = 8 can make the code not compile on DX11 if the texture layer resolution is less than 2^7

To ensure sanity, I think the MipLevels should be a custom preprocessor, with a default to 1 and a tooltip on how to set up proper MipLevel for each layer