* plc-kml.py has now a few options for setting marker icons

* plc-kml.py has now a few options for setting marker icons
* this required a tweak in plcsh, that did not handle the command line
    very nicely when invoking another script file.
it is now possible to
* write a script foo.py and mention in 1st line: #!/usr/bin/env plcsh
* invoke foo.py with options and args like this
$ foo.py [plcsh-options] -- foo-options and args
* rightly get foo.py's help by running
$ foo.py --help

this is still not perfect as I'd rather remove the need for the extra --
but it's already better than before