Altered code to properly handle asymmetric twin swing dice

Fixes #1467.

http://jenkins.buttonweavers.com:8080/job/buttonmen-blackshadowshade/555/
Do we really want 'Twin' to be in 'properties' in the API?  For everything else in the API, we use:
* skills: persistent die skills
* properties: transient die attributes based on some recent activity

It's not clear where in there die types would go, but my inclination is to think that it's another kind of thing: in the long run, we want the backend to tell the UI whether something is a swing or option die, rather than the UI parsing the recipe.  So basically i would expect this to be encoded as: `types => array('Twin')` within `activeDieArray`.

What do you think?  In particular: (a) what do you think the right answer is, and (b) is there a reason not to jump to the right answer now?  (There may well be.)