[Space Shooter] Player Healthbar

[GSoster]

Add a player healthbar that also displays the shield value. Right now the player is destroyed if touched by an enemy/asteroid without a shield.

[GSoster]

Tasks to make player healthbar possible:

• add health attribute to player
• add health slider to HUD
• update enemy shot contact logic to decrease players health instead of destroying it

[GSoster]

This is on hold until the HUD system is restructured: #10