Sprint 3 Milestone Merge

Added the following features:

   * Capturable pillboxes and bases
   * Tank death and respawns
   * Destructible environments
   * Engineer pathing (not implemented in demo)
   * Animated and functional bases
   * Tank invisibility in trees
   * Tank mine laying, explosions, invisibility to enemies
   * Improved start game UI, networking functionality
   * Terrain speed modulation
   * Ammo and mine parameters for Tanks
   * General game polish and system finalization
   * Improved multi-user support
   * Start game lobby, with chat support