#8 Add support for processing reltables

[Susan Salituro]

(This is closely related to feature request #2824914, I think.)

Our documentation team makes extensive use of reltables for creating related links lists. This information is currently being discarded by dita2wiki. It would be great if dita2wiki were able to process reltable data and output wiki text.

See related support discussion at https://sourceforge.net/projects/dita2wiki/forums/forum/864449/topic/3541672.