handle empty responses

provide predefined errors with the corresponding error messages from …

…rigctl

add support for set_level BAND_SELECT

add support for lock mode and retrieving the KEYSPD

hamlib request also fail if there was a hamlib error code returned

upgrade dependencies

add support for morse code transmissions

Merge pull request #1 from w9cf/master

Replaced newlines with separator character so that tciadapter obeys the |f etc. rigctld protocol.