Added isReversing() method.
Increased reversespeed on test DefaultTank.
Tank now correctly turns while reversing..

..also tank test sprite rotation is based on the tank model.
Fixed turnSpeed while reversing.
Added turretPos and a turret for the AbstractTank class. Also tried to create proper rotation for the turret. (WIP)
Reworked turret.
Trying to Turret move nicely with Tank...
The turret direction in AbstractTurret is now detemined by a float instead of a vector.
The turret now rotates accordingly to the mouse. An image of a turret is now drawn at the tank's center position.
Spellcheck on a comment
Tweaking Tansk.
Added javadoc to entity and some other minor changes.
Fixed turret direction (angle).
Added JUnit tests for Entity and MovableEntity.
Added javadoc for Entity and MovableEntity. Also deceleration if now called friction.

ReverseSpeed has also been removed since it wasn't used.
AbstractProjectile, Abs.Tank, DefaultTank no longer require a reverseSpeed.
Fixed a bug where the turret would add its rotation instead of updating it. Also fixed so that the turret also follows the mouse while the mouse is clicked.
Added data-folder with basic sprites.
Overall cleanup.

Enitity is now abstract.
Reworked tank and turret.