Landmine improvements

[farooqkz]

I think we need to improve landmines further:

• If a player's head clashes with a landmine, the mine will be activated.
• Increase landmine damage radius so if someone clicks on it, they will get damaged anyway(see next task)
• Make landmine damage proprotional to distance of players from landmine. The further the less damage.
• Add a recipe for landmine. 4 iron + 4 coal
• Landmines can be placed at the ceiling if the player is pointing to bottom of a block when they are placing it. Useful for tunnels.