Feat: HTML from WYSIWYG editor - new image widths 1/6th and 1/8th and use Css variables

[iJungleboy]

I'm submitting a

[x] feature request

...about

[x] edit experience / UI
[x] Razor templating

Current Behavior / Expected Behavior

ATM the wysiwyg has 100%, 50%, 25% 33%, 66% etc. but it's missing 1/6th and 1/8th.

It's also using hard-wired values, so we want to move to CSS variables for gutters.

Your environment

• 2sxc version(s): 17.10