Create basic items mechanism in the serverside and load the items database

[gioragutt]

Depends on #24, which describes all the items in the game and their effects (the actual "implementation" of the json is subject to change to fit parsing needs and whatever's necessary to make the mechanism support all the effect kinds).

This should basically load the json db and parse it into models that can be used to do game logic.

• Create suitable models (without effects)
• Load the json db on server startup
• Propose a design of how to keep the items state on players in the game.

Regarding the 3rd point - remember that the items are also droppable by mobs and stuff,
So this "Items Database" should be a fairly abstract detail - it shouldn't actually be what IS in a game, but what CAN be in a game.