Remove core dependencies from CScript

As an ongoing effort to break out script verification. I hope this doesn't conflict with @sipa's or @jtimon's next steps.

This work moves the logic for writing custom core classes to scripts out of CScript. Those classes can describe how their data should be written to a script, and CScript does so without further knowledge.

Please ignore the entire PR's diffstat while reviewing as it won't be at all helpful. Individual commits will make much more sense.

Also, CScriptBinaryData is a pretty terrible name but I couldn't come up with anything better. Suggestions welcome.
Is this necessary to be virtual and overridable? Just having a templated method/constructor that takes any type, and copied the vector from x.begin() to x.end() seems like it would suffice. This is really just convenience - the user of CScript can always use his own code to first convert to a vector.