separate YACLML code from main code

The YACLML renderer is now a separate component. It does not get
compiled with the SML system. Include it manually with SML+YACLML
projects.

Example:

 (<sml-render '("Paragraph"
                (:h1 "Header 1")
                (:h2 "Header 2")
                (:table ((:th "Header 1" "Header 2")
                         (:td "Data 1" "Data 2")))
                (:ul ("Data 1"
                      ("Data 2"
                       "Data 3")
                      "Data 4"))))