Improve Pi Non-GPU-accel exposure (#148)

Changes exposure setters to accept a floating point input (rather than integer)
Updates the UI to change exposure in increments of 0.1 (rather than 1.0)
Updates quirky PI camera logic to use the raw_ interface with scaling/offset logic matching the GPU-accelerated pi3 camera logic from Declan.
Adds logic to disable auto-white-balance in the PI camera, which should yield more consistent vision processing results.

photon-server/src/test/java/org/photonvision/vision/processes/VisionModuleManagerTest.java

@@ -69,7 +69,7 @@ public class VisionModuleManagerTest {
         }
 
         @Override
-        public void setExposure(int exposure) {}
+        public void setExposure(double exposure) {}
 
         @Override
         public void setBrightness(int brightness) {}