Add a new renderer/technique that can render multiple blocks in a single pass is needed

[bilgili]

Current renderer as stated in #228 is slow if there is transparency and large number of blocks.

• A new renderer/technique is needed for rendering multiple blocks at a single pass.
• Has to look at empty space skipping with current implementation. If it is easy, it can improve rendering speed and memory.

@chevtche is already working on an OpenGL 4 based renderer possibly based on "http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6231628&tag=1"