Allow opcap to receive flags and arguments from a file

[acmenezes]

As opcap gains new features and becomes more complex being capable of reading a configuration file may be an important step to fine tune the audits. One good application for that is thinking about those configuration files as profiles. For example we could have a full audit for all levels and capabilities, an audit targeting only failed operators, an audit targeting only specific tests etc. With that it becomes easier to run audits and we can provide a ready to use recipe for new comers to try opcap.