Load sheet data from vtex json
Load from sheet data if we have more than 1 image
Trim the bullshit from vtex json, we only care about 2D and sprite sheets for now
Creating texture through context menu with multiple selected textures creates sheet
Custom button drawing for list property so they don't look awful
If we open editor with vtex with dmx encoding, just create empty texture file
Property sheet target can now just be the texture file
Only mark as modified if json has changed