[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.

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/armbotoffboard/ExampleSmartMotorController.java

@@ -93,7 +93,4 @@ public class ExampleSmartMotorController implements SpeedController {
 
   @Override
   public void stopMotor() {}
-
-  @Override
-  public void pidWrite(double output) {}
 }

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/drivedistanceoffboard/ExampleSmartMotorController.java

@@ -97,7 +97,4 @@ public class ExampleSmartMotorController implements SpeedController {
 
   @Override
   public void stopMotor() {}
-
-  @Override
-  public void pidWrite(double output) {}
 }

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/elevatortrapezoidprofile/ExampleSmartMotorController.java

@@ -93,7 +93,4 @@ public class ExampleSmartMotorController implements SpeedController {
 
   @Override
   public void stopMotor() {}
-
-  @Override
-  public void pidWrite(double output) {}
 }

wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/examples/pacgoat/subsystems/Pivot.java

@@ -65,7 +65,7 @@ public class Pivot extends PIDSubsystem {
   /** Set the motor speed based off of the PID output. */
   @Override
   protected void usePIDOutput(double output) {
-    m_motor.pidWrite(output);
+    m_motor.set(output);
   }
 
   /** If the pivot is at its upper limit. */