Simplify Sendable interface (#1864)

This removes the name and subsystem from individual objects, and instead
puts this data into a new singleton class, SendableRegistry.  Much of
LiveWindow has been refactored into SendableRegistry.

In C++, a new CRTP helper class, SendableHelper, has been added to provide
move and destruction functionality.

Shims for GetName, SetName, GetSubsystem, and SetSubsystem have been added
to Command and Subsystem (both old and new), and also to SendableHelper to
prevent code breakage.

This deprecates SendableBase in preparation for future removal.

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

@@ -10,9 +10,13 @@
 #include <hal/Types.h>
 
 #include "frc/SolenoidBase.h"
+#include "frc/smartdashboard/Sendable.h"
+#include "frc/smartdashboard/SendableHelper.h"
 
 namespace frc {
 
+class SendableBuilder;
+
 /**
  * DoubleSolenoid class for running 2 channels of high voltage Digital Output
  * (PCM).
@@ -20,7 +24,9 @@ namespace frc {
  * The DoubleSolenoid class is typically used for pneumatics solenoids that
  * have two positions controlled by two separate channels.
  */
-class DoubleSolenoid : public SolenoidBase {
+class DoubleSolenoid : public SolenoidBase,
+                       public Sendable,
+                       public SendableHelper<DoubleSolenoid> {
  public:
   enum Value { kOff, kForward, kReverse };