help for comterp keyword arguments

[vectaport]

The comterp help command should be extended to provide documentation for each keyword argument of a command. For example, help(substr) returns:

str=substr(str n|str :after :nonil) -- extract characters from a string (:nonil returns string if no match)

and help(substr(:after)) could return:

:after returns string after match

In addition help(substr :all) could list all the keywords, plus the original string of documentation (as could help(:all)). This could be implemented with a ComFunc::docmap() which returns a key/value dictionary of keywords paired with keyword documentation strings.

[vectaport]

Done for comterp using new virtual function virtual char** ComFunc::dockey() which returns a nil-terminated array of keyword documentation strings.

Needs to be done for comdraw, graphdraw, flipbook, and drawserv.

[vectaport]

Done for comdraw, graph draw, flipbook, and drawserv.