Add check to ensure correct parameters are passed to rules

[daltonmatos]

Currently all rules requires one parameter. This parameter is passed with the --ruleparam CLI argument. The problem is that when this argument is not passed, the rule is called with (None,). This is specially dangerous for the oltderthan rule, because with None as a rule parameter it will potentially delete all container content.

This happens because any integer returns True when compared do None, so:

    ...
    delta = (datetime.now() - objdate)
    return delta.days > ndays

When ndays is None this will always return True.