Namespace all wpilibc functions/classes into "frc" namespace. (#311)

Base.h provides a backwards compatibility shim (enabled unless
NAMESPACED_WPILIB is defined) that does a "using namespace frc".
However, as some header files do not include Base.h, this may
be a breaking change in some corner cases (with an easy fix).

Fixes #218.

wpilibc/athena/include/Vision/BinaryImage.h

@@ -18,6 +18,8 @@
  */
 #include "Vision/VisionAPI.h"
 
+namespace frc {
+
 class BinaryImage : public MonoImage {
  public:
   virtual ~BinaryImage() = default;
@@ -42,3 +44,5 @@ class BinaryImage : public MonoImage {
   static bool CompareParticleSizes(ParticleAnalysisReport particle1,
                                    ParticleAnalysisReport particle2);
 };
+
+}  // namespace frc