Implements mixins and namespace support

[jdigger]

Implemented basic mixin support in NodeImpl

Implemented basic NamePathResolver and NamespaceRegistry support in SessionImpl

Fixes #6

[jdigger]

@hsfear @sagarsane Please review.

[sagarsane]

Minor : Could idx++ be in the for statement itself?

[hsfear]

I generally avoid style comments, but I will admit that even in Java, I would be include to use a list for newValues and convert back to an array at the end.

I will also note that you don't need idx here so you could probably use a foreach here with newIdx being a counter initialized before the loop begins.

That would also allow you to ditch the found flag, you can just compare newIdx to the size of the original array.