Moving player existance information into player object.
Layering clouds.
Removing existing explosions. Explosions will be handled by the entity in future.
Renaming "_populateArena" to "_spawnEntities".
Randomising the spawning of enemy entities.
Moving data object in player.

Making the data object unique per instance so that multiple players can
be tracked.
Adding score and level into data object for instance tracking.
Removing level set, as it's now handled by the setData method.
Moving hud rendering into a module.
Moving spawn entities into the calculation schedule.
Moving pause message to the hud as that is it's logical location.

Added optional stroke to text rendering.
Merge branch 'modularisation'

* modularisation:
  Moving pause message to the hud as that is it's logical location.
  Moving spawn entities into the calculation schedule.
  Moving hud rendering into a module.
  Removing level set, as it's now handled by the setData method.
  Moving data object in player.
  Randomising the spawning of enemy entities.
  Renaming "_populateArena" to "_spawnEntities".
  Removing existing explosions. Explosions will be handled by the entity in future.
  Layering clouds.
  Moving player existance information into player object.
  Adding intro text to the constant arena object.
  Removing a lot of the constant data from main class.
  Removing commented out code.
  Redesigning constants object.