[wpilib] Remove PIDController, PIDOutput, PIDSource

Move them to the old commands vendordep so that PIDCommand and PIDSubsystem
continue to work.

This also removes Filter and LinearDigitalFilter.

wpilibc/src/main/native/include/frc/Encoder.h

@@ -11,7 +11,6 @@
 #include "frc/Counter.h"
 #include "frc/CounterBase.h"
 #include "frc/ErrorBase.h"
-#include "frc/PIDSource.h"
 #include "frc/smartdashboard/Sendable.h"
 #include "frc/smartdashboard/SendableHelper.h"
 
@@ -40,7 +39,6 @@ class DMASample;
  */
 class Encoder : public ErrorBase,
                 public CounterBase,
-                public PIDSource,
                 public Sendable,
                 public SendableHelper<Encoder> {
   friend class DMA;
@@ -314,8 +312,6 @@ class Encoder : public ErrorBase,
    */
   int GetSamplesToAverage() const;
 
-  double PIDGet() override;
-
   /**
    * Set the index source for the encoder.
    *