#6 LWRRod and MaterialBlock: Store MAterialBlocks in TreeSet and Compareto

[Scott Forest Hull II]

Store the MaterialBlocks on LWRRod as a treeset and use the comparable interface to order the "positions" correctly on the Z axis (so they are ordered when they are pulled off the LWRRod).

The compareTo operator should just return the pos stored on the class.

Fix for Java. I dont think this is possible for C++ side.