feature request: better error messages

[pengnam]

As one of two users of SOC print, I believe my opinion carries some weight.

The new SOC print expects the users to indicate the duplex along with the printer name. I failed to do so and it does not indicate that the printer I specified is not in printer list. Please fix.
To recreate, the command I used is below.

[pengnam]

@dlqs For your information.

[dlqs]

Hello, valued customer! Thank you for contacting support@socprint.sh. Since our dear PM is on marital leave (SOCPrint's benefits include 3 days marital leave and 21 days paid vacation), I will take this issue.

According to the docs by our printer provider, a printer name with no suffix e.g. psts should work. But upon triage, it does indeed appear that only psts-dx works.

Since our all-knowing, omnipotent printer provider couldn't possibly have misdocumented things, I suggest the following:

1. Change list command regex at https://github.com/dlqs/SOCprint/blob/master/socprint.sh#L227 to exclude printers without suffixes
2. Change the print command to use the list command to list valid printqueues and,
3. Flash a warning if the printqueue doesn't exist in said list (but still continue with the rest of the command)