Update LiveWindow to provide continuous telemetry. (#771)

LiveWindow.updateValues() is now called from IterativeRobotBase on every
loop iteration.  Telemetry for all WPILib classes is enabled by default;
it can be disabled for specific classes using LiveWindow.disableTelemetry(),
or all telemetry can be disabled using LiveWindow.disableAllTelemetry().

This necessitated changing the hook methodology into other classes to
be more property-based rather than each class providing multiple functions.
This had the benefit of reducing boilerplate and increasing consistency.

- Remove NamedSendable, add name to Sendable.

- Provide SendableBase abstract class.

- Deprecate LiveWindow addSensor/addActuator interfaces.

- Add LiveWindow support to drive classes.

- Add addChild() helper functions to Subsystem.

- Fix inheritance hierarchy.  Now only sensors inherit from SensorBase.
  Other devices inherit from some combination of SendableBase, ErrorBase, or
  nothing.

wpilibc/src/main/native/include/Counter.h

@@ -8,16 +8,13 @@
 #pragma once
 
 #include <memory>
-#include <string>
 
 #include <HAL/Counter.h>
 #include <HAL/Types.h>
 
 #include "AnalogTrigger.h"
 #include "CounterBase.h"
-#include "LiveWindow/LiveWindowSendable.h"
 #include "SensorBase.h"
-#include "networktables/NetworkTableEntry.h"
 
 namespace frc {
 
@@ -33,9 +30,7 @@ class DigitalGlitchFilter;
  * All counters will immediately start counting - Reset() them if you need them
  * to be zeroed before use.
  */
-class Counter : public SensorBase,
-                public CounterBase,
-                public LiveWindowSendable {
+class Counter : public SensorBase, public CounterBase {
  public:
   enum Mode {
     kTwoPulse = 0,
@@ -53,7 +48,7 @@ class Counter : public SensorBase,
           DigitalSource* downSource, bool inverted);
   Counter(EncodingType encodingType, std::shared_ptr<DigitalSource> upSource,
           std::shared_ptr<DigitalSource> downSource, bool inverted);
-  virtual ~Counter();
+  ~Counter() override;
 
   void SetUpSource(int channel);
   void SetUpSource(AnalogTrigger* analogTrigger, AnalogTriggerType triggerType);
@@ -96,11 +91,7 @@ class Counter : public SensorBase,
   int GetSamplesToAverage() const;
   int GetFPGAIndex() const { return m_index; }
 
-  void UpdateTable() override;
-  void StartLiveWindowMode() override;
-  void StopLiveWindowMode() override;
-  std::string GetSmartDashboardType() const override;
-  void InitTable(std::shared_ptr<nt::NetworkTable> subTable) override;
+  void InitSendable(SendableBuilder& builder) override;
 
  protected:
   // Makes the counter count up.
@@ -115,7 +106,6 @@ class Counter : public SensorBase,
  private:
   int m_index = 0;  // The index of this counter.
 
-  nt::NetworkTableEntry m_valueEntry;
   friend class DigitalGlitchFilter;
 };