Refactor taocp commands and sub-commands

[wallberg]

a) save a copy of the *flags.Command generated by AddCommand(); removes the need to run parser.Find()

b) rename fooBarCommandType to fooBarCommandDataType

c) stop saving the fooBarCommandDataType to a variable; it is unused

See the forthcoming 'cu' command and sub-commands as examples.

Copied from wallberg/sandbox#4