Added pause-button and moved healthbar
Modified the pause-menu

The itemview now hides/show when pausing/unpausing. Also, the game
fully stops when you pauses.
The gamescreen is now partially hidden when you pause
Updated the pausemenu

In the pausemenu you can now move items from the main inventory to the
QuickSelection. A lot of comments wa also added.
Updated itemView

You can now move items between QuickSelection-slots
Merge branch 'itemmenu' into develop

Conflicts:

zombie-world/src/se/glory/zombieworld/model/entities/items/Healthbar.jav
a

zombie-world/src/se/glory/zombieworld/model/entities/items/QuickSelectio
n.java

zombie-world/src/se/glory/zombieworld/model/entities/weapons/WeaponArsen
al.java
	zombie-world/src/se/glory/zombieworld/screens/GameScreen.java
	zombie-world/src/se/glory/zombieworld/utilities/Constants.java