Start implementing ray-casting.

This adds a QueryPipeline structure responsible for scene queries.
Currently this structure is able to perform a brute-force ray-cast.
This commit also includes the beginning of implementation of a SIMD-based acceleration structure which will be used for these scene queries in the future.

src/pipeline/mod.rs

@@ -3,7 +3,9 @@
 pub use collision_pipeline::CollisionPipeline;
 pub use event_handler::{ChannelEventCollector, EventHandler};
 pub use physics_pipeline::PhysicsPipeline;
+pub use query_pipeline::QueryPipeline;
 
 mod collision_pipeline;
 mod event_handler;
 mod physics_pipeline;
+mod query_pipeline;