Updated Tw2ValueBinding
Updated Tw2ValueBinding

- Made some changes to `Tw2ValueBinding` which makes it easier to get information from the binding once it has been initialized. The changes are backwards compatible and cause no extra processing during Initialization, but can do so when dealing with them later.

- Changed default `_sourceElement` and `_destinationElement` properties to be `null` by default.  This makes it possible to figure out if the source or destination has been swizzled (previously they defaulted to 0 which meant you couldn't be 100% sure they were )
- Changed private variables `srcIsArray` and `destIsArray` to constructor properties (makes it easier to tell if the source and destinations are arrays without checking the objects and their attributes, this calculation was already done privately)
cppctamber/ccpwgl,ccpgames/ccpwgl