Moved C++ comments from source files to headers (#1111)

Also sorted functions in C++ sources to match order in related headers.

wpilibc/src/main/native/cpp/PIDSource.cpp

@@ -9,11 +9,6 @@
 
 using namespace frc;
 
-/**
- * Set which parameter you are using as a process control variable.
- *
- * @param pidSource An enum to select the parameter.
- */
 void PIDSource::SetPIDSourceType(PIDSourceType pidSource) {
   m_pidSource = pidSource;
 }