Norbert - Block Types

Redesigned the terrain generation so that each block of a block type has its own unique properties. Game remembers which block you are picking up, so that you can now move around blocks of the same type that look a certain way. This opens the door for similar dirt blocks that can provide different gameplay experiences (such as dropping items or impacting movement speed, dig speed, jump height).
Also improved the visuals for carrying a block, removed the ugly dirt sprite I had before and just opted to use the existing block sprite that was picked up. This helps track what you're holding better, and lessens the load when I want to include new blocks/items.
Changed the name of the game to Norbert. I knew a field mouse name Norbert once, it seems fitting.