Add items

Resolves #88 (closed)

Added item types:

• Dice, for moving along the board
• Trap, can be placed on the board and is triggered when a player lands on it
• Action, item can be activated

Currently there is still a bug, which causes the material of a trap to not be applied to the node, which it was placed on. (fixed)

The serializing/deserializing could be improved too