Some art assets updated. Bug and balance tweaks.

Added new Elite model and updated some mechanics for them. Added new Ghost model and refined balancing. Other bug fixes and adjustments.

New models for ODSTs, Wraith Tanks, Hunters and some props. Reworks of the aforementioned units including new variants of each. Added Sentinels as hostile indiginous units which spawn from Forerunner structures. Visual and QoL improvments to the user interface.