Upgrade to SD v2, add txt2img for empty canvas, disable safety checker

[micimize]

Am not attached to any of the details here – just thought I'd PR what I needed to do to get things working.

Am going to experiment with some of the other plugins floating around, like https://github.com/Interpause/auto-sd-paint-ext and https://github.com/w4ffl35/krita_stable_diffusion

[nousr]

i think instead of loading two pipelines you can save vram by storing the individual components and then compiling the necessary pipeline at runtime, if you want to do this i would gladly merge!