lua: allow for real booleans in "needs" expression

lua: allow for real booleans in "needs" expression

In addition to

    function init (args)
        local needs = {}
        needs["dnp3"] = tostring(true)
        return needs
    end

allow for

    function init (args)
        return {dnp3=true}
    end

with the idea that the former will be completely removed for 8.0.

This works with all existing SV tests and as a string value, any value
is considered "truthy".