Dplug v16

[p0nce]

• [ ] I think dplug:au, dplug:clap, dplug:vst3, dplug:vst2, dplug:flp, and maybe dplug:client could be merged without too much adverse effects. Those compilations are conditional anyway.
• [ ] Do #915
• [ ] Remove box3 since used nowhere (in a plugin)
• [ ] deprecate convertImageRefToPNG
• [ ] Make futurePBREmissive default