[css-lists-3] Trimming down Lists 3 featureset

Given the recent discussion on emdash list markers and the CR publication
of CSS Counter Styles, I was thinking it might be a good idea to rev Lists.
The very unstable parts are the positioning and layout rules, but we could
defer those and just keep the other things, i.e. CSS2.1 with the addition of

   * display: inline-list-item
   * defining list numbering in terms of the implied 'list-item' counter
   * list-style-image: <image> | none
     (instead of list-style-image: <url> | none)
   * list-style-type: <counter-style> | <string> | none
     (instead of list-style-image: <css21-defined-counters> | none)
   * font/color marker styling by reference to ::marker in Pseudo Elements L4
   * counter-set property

or some subset thereof. What do people think?

~fantasai