More robust error handling for .dm command

Enhanced .dm to detect several error situations and issue error message
rather than terminating with Python stack trace:
(1) .dm without a macro name
(2) missing .dm- (either hit another .dm or end-of-file)
Merge pull request #32 from wf49670/develop

More robust error handling for .dm command
.dv command
Merge branch 'develop' of https://github.com/rfrank/ppgen into develop

merging Walt's updated develop from github
recoding .ma parsing
version 3.36