Move the ckecks for nmc_arg_is_help to the beginning of the
checks for command matches.

Up to now, no command begins with 'h', so this has no behavioral
change whatsoever. But imagine a command that begins with 'h'
(for example `nmcli general hostname`), in that case `nmcli general h`
should still show the help, as users might be accustomed to this
abbreviation.

Signed-off-by: Thomas Haller <thaller@redhat.com>

Wouldn't make a ton of sense to print "started" for the STARTING
property if NM wasn't running.

It says 'starting' when NM is in the process of startup (still activating
connections); 'started' when NM finished the startup.

Setting the logging level fails for normal users due to missing dbus
permissions as configured in src/org.freedesktop.NetworkManager.conf.

In that case, nmcli simply fails showing the dbus error. This error
is however not very clear, so this commit shows a different error
text for the particular case of ACCESS_DENIED.

Signed-off-by: Thomas Haller <thaller@redhat.com>

no actual change

The data are added to output_data at first, and then they are printed all at
once using print_data(), that takes care of proper alignment and display.

The static 'width' values defined in NmcOutputField columns are not used now,
but dynamically computed maximal widths override them.

That way it is not displayed by default:
$ nmcli general status

But can be explicitly requested:
$ nmcli -t -f running,version general status
$ nmcli -f all general status

E.g. Fedora initscripts do this in
/etc/sysconfig/network-scripts/network-functions

is_nm_running ()
{
    [ "$(LANG=C nmcli -t --fields running nm status 2>/dev/null)" = "running" ]
}