XRENDERING-297: Add Markdown Syntax 1.1 with macros, superscript and subscript support
* Don't bundle Markdown syntaxes in XWiki Enterprise because they depend on pegdown 1.4.1 which brings parboiled-java 1.1.5 which duplicates classes of one of its dependencies (parboiled-core 1.1.5) and thus fails the build and the release. We can bundle Markdown syntaxes in 5.2 final if we fix the problem in the mean time.