resolves #469, #364, #472 list improvements

- support additional list numeration and markers
  * lowergreek and decimal for ordered lists
  * disc, square, circle for unordered lists
- fix missing style when role shorthand is used on ordered list
- convenience method for retrieving list marker keyword
Merge pull request #473 from mojavelinux/ordered-list-numeration

resolves #469, #364, #472 list improvements