It is better to have a class to store the parameters into a class attribute.

If we import the functions directly we are not able to mock the method
it in the proper way as in the previous commit:
 - 2cb7a0f5

Check if the signature_private_key_file is well handled during the argument parsing.

You can use the slapgrid scripts without providing the signature_private_key_file.

This argument must work just as instance root parameter.
Well, it can be provided by command line and by slapos configuration file.
 - command line: signature-private-key-file=/path/to/the/file
 - slapos configuration file: signature_private_key_file=/path/to/the/file

Additionaly fix small issue with test assertions.

Mock netifaces in order to simulate real behaviour of machine. Add another
part of "persistence", which allows simulation of network stack.

Make test more flexible and controlallbe by exposing groups.

Additionally add required "persistence" to test.

Duplicate Listbox_asHTML from xhtml skin in vifib_hosting_theme, change checkbox buttons to radio buttons.