Revised precaches for player models.
Added sounds for sapper.
Implemented vehicle system base.
Fixed issues that occured when switching team.
Reverted changes for commander view.
Removed single-player content.
Removed some unused HUD interfaces.
Added new player sounds.
Threw in medic model from Team Fortress 2 for revision, as it's fairly close to the Invasion model.
Begun updating class descriptions.