Added REFERENCES field to MR::App

The REFERENCES field allows the developer to indicate the articles that should be cited whenever a particular command is used.
If specified, the contents of REFERENCES will appear at the bottom of the help page.
Added relevant references to a range of commands

Not necessarily a complete commit, others will need to review the list of commands and add references as they see fit.
Minor cleanup of references for various commands

Also fixed AUTHORS -> AUTHOR typo in a couple of commands
Merge branch 'references'

Conflicts:
	cmd/tckmap.cpp