Port to new glow and glow-extras, start windowed by default

.gitmodules

Flock/extern/CMakeLists.txt

Flock/extern/glm

Flock/extern/glow

Flock/extern/glow-extras

Flock/flock/CMakeLists.txt

Flock/flock/generated/.gitignore

Flock/flock/shader/opaque/litOpaque.fsh

Flock/flock/src/FlockApp.cc

Flock/flock/src/FlockApp.hh

Flock/flock/src/camera/FollowCameraController.hh

Flock/flock/src/instancing/InstanceGroup.cc

Flock/flock/src/instancing/InstanceGroup.hh

Flock/flock/src/instancing/InstancingManager.cc

Flock/flock/src/instancing/InstancingManager.hh

Flock/flock/src/logic/gameplay/GameState.cc