Fix up output and error displaying in commands

Fix up output and error displaying in commands

Fix up output and error displaying in commands so far implemented.  Replace
usage of print() with output() and outputf() for normal operation and error()
for error display.  debug() is replaced with verbose() which is contingent on
the -verbose switch.

Also add error handling to a number of commands.

Signed-off-by: David Howells <dhowells@redhat.com>