Temporary pictures of tank spawnpoint/powerup spawnpoint
Added an AbstractSpawnPoint that has a spawnable boolean and a position
A powerup factory has been added

The first method returns a powerup object based on a String. The second
method returns a random powerup object.
A class for powerup spawning

The class checks if any powerups are currently in its place. It there
aren't any, it is spawnable. When the timer runs out in the update
method a new powerup spawns depending on the SpawnPoint's type.
A class for the spawn position of a tank

The only thing this class has is a position, shape and spawnable check.
This class is used from the TankSpawner class. The object is merely
used for keeping track of a position and if a tank may spawn on it.
Moved the current, and only tank, to a new package
A factory for tanks

Very similar to the PowerupFactory, but instead of a String, this
factory only takes a Player object as an parameter. Also, the
DefaultTank should be adjusted.
A class that keeps track of what the players that needs tp spawn

The idea is simple. It's a singleton class that the Player objects call
when their tanks are destroyed. They are then added to a list of Player
objects that are spawned according to a timer.
The class also holds the TankSpawnPoints.
Adjusted the Player class for tank spawning

The Player class no holds lives, respawntime and a type of tank (might
want to change this).
AbstractTank now takes a Player object as a parameter
Added null checks to Play and also added some tank and powerup spawnpoints

An additional change was that movableEntity is the only thing being
checked for collision. This has been edited since AbstractSpawnPoint
for example not a moving entity but needs to be checked anyway.
Checking collision for Entity aswell and not only MovableEntity

This is for the SpawnPoints to work properly.
The powerups are now deactivated if the tank is destroyed
Changed the powerups to be spawned, for testing
Moved the effectActive so that powerups deactivates correctly
Simple null check to avoid exceptions when a tank dies
Removed an unnecessary sysOut
The shield powerup is now correctly deactivated

The updateEffect now checks if the shield is active. If it isn't
active, the powerup itself deactivates, otherwise it moves the shield.
The shield now keeps track of the tank it is shielding and has health

The purpose of this is that the projectiles fired from the tank, that
has the shield activated, shouldn't damage the shield.
Removed an unused import