Add version flag and show help message for unknown arguments

[shv-ng]

frec currently has no simple way to check the version, and it gives unclear messages when unknown flags or commands are used.

Examples:

$ frec -v
Incorrect Usage: flag provided but not defined: -v

$ frec version
No help topic for 'version'

It would be useful to support common version commands like:

$ frec -v
$ frec --version
$ frec version

Also, when unknown flags/commands are passed, frec should show a helpful message or the help output instead of just an error.