Add default policy-name function

[koparasy]

In Action, Policy, basically every abstract layers with a method name(), we could have something like that by default:

    virtual const char* name() const {
        // +1 to remove the first character which is the number of letters in the name (C++ default)
        return typeid(*this).name()+1;
    }

Users could override it but at least all the tests etc would be simpler.

Originally posted by @lpottier in #183 (comment)