topic/snacman#82 paper bill score

[Adnn]

closes #82.

• Make each player hud a distinct Entity.
• Move the score to world space.
• Add the powerup text line.
• Remove unused parameter from add*GeoNode().
• Add billpad model under score and powerup texts.
• Implement a (hackish) scene editor.
• Refine positionning of the paperbill hud thanks to scene editor.
• Shorten power-up names.
• Reverse order: player entity is pointing to the hud entity.
• Refactor the billpad to be manually added to the scene graph. Allow to corretly remove the hud with the player.
• Change HUD font.
• Fix removal of paperbill and reset of player state between rounds.
• Scale down powerup text.
• Fix snacman#83: player moves along direction pressed in previous round.
• Count won rounds, and display them in billpad.
• Fix snacman#84: Reorder round monitor after eatpill.