New library 'property2'

The new library for managing objects, object templates and their properties is coming along well. Mostly, it's conversion from a prototype. The library may eventually extend or replace yake::ent depending on how well it fares over the next few releases.

Today, the first physics demo has been implemented (and will be in SVN after a bit of cleanup work).

Quite a few bugfixes will make their way into the codebase, too.

When these changes have been committed to SVN, then it's time to update the Lua bindings for this library. This will be quite interesting, I think. I used the object browsing capabilities of yake::property2 to save the object database by generating a Lua script on-the-fly which, when run again, will re-create the objects and their properties.

Note, that the code for this library lives in a separate branch (“yake2”).