Added craftable gun mods that will modify your attack. More interesting mods later.

• Topaz - allows multi-directional firing; firing is now possible up and down.
• Ruby - damage modifier
• Diamond - splits your blast
• Emerald - fires a beam instead of a blast
• Amethyst - knock-back

All these are craftable from the crafting table.

Added new materials and recipes:

• coal + coal smelted now becomes oil (used to be carbon; carbon moved to compressor)
• oil + oil smelted now becomes plastic
• plastic + gold_bar now becomes computer_chip
• In a crafting bench, 4 computer chips + a gem become a mod

Added a compressor.

• coal + coal is carbon
• dirt + dirt is coal
• carbon + carbon is a diamond