new `slapos console script.py`style invocation
To execute a slapconsole script, we could only do:
slapos console < script.py
but this does not stop in case of error
or
echo 'execfile("script.py")' | slapos console
but this is too complicated.
Extend this API so that we can simply use
slapos console script.py
inspired by python script.py