Use an array instead of string for command

[fcoelho]

Using an array makes it unecessary to escape strings for arguments, as the child process receives each element in the string as a separate argument regardless of its contents.

I have to use printers that are accessible via USB and have URIs with characters such as "&". Instead of trying to quote everything, this just sends the strings as arguments directly, no quoting needed anywhere.

[jking916]

All tests passed on my end. Merging this in.