Remove "iPhone" wording and use more general term "iOS device" in error message
Use an enum and a single variable for determining command to run
Print error if user attempts to supply multiple command arguments
Print error if no command was supplied
Swap "-u" and "-U" arguments and print deprecation warning if still used

All other tools around the libimobiledevice stack use a lower case
"-u" argument to specify a target UDID. This change swaps the "--uninstall"
and "--udid" argument short form to provide consistency while allowing
the use in the old way as a fallback.