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/Commands/Subsystem.h

@@ -8,49 +8,50 @@
 #pragma once
 
 #include <memory>
-#include <string>
+
+#include <llvm/StringRef.h>
+#include <llvm/Twine.h>
 
 #include "ErrorBase.h"
-#include "SmartDashboard/NamedSendable.h"
-#include "networktables/NetworkTableEntry.h"
+#include "SmartDashboard/Sendable.h"
+#include "SmartDashboard/SendableBase.h"
 
 namespace frc {
 
 class Command;
 
-class Subsystem : public ErrorBase, public NamedSendable {
+class Subsystem : public ErrorBase, public SendableBase {
   friend class Scheduler;
 
  public:
-  explicit Subsystem(const std::string& name);
-  virtual ~Subsystem() = default;
+  explicit Subsystem(const llvm::Twine& name);
 
   void SetDefaultCommand(Command* command);
   Command* GetDefaultCommand();
+  llvm::StringRef GetDefaultCommandName();
   void SetCurrentCommand(Command* command);
   Command* GetCurrentCommand() const;
+  llvm::StringRef GetCurrentCommandName() const;
   virtual void Periodic();
   virtual void InitDefaultCommand();
 
+  void AddChild(const llvm::Twine& name, std::shared_ptr<Sendable> child);
+  void AddChild(const llvm::Twine& name, Sendable* child);
+  void AddChild(const llvm::Twine& name, Sendable& child);
+  void AddChild(std::shared_ptr<Sendable> child);
+  void AddChild(Sendable* child);
+  void AddChild(Sendable& child);
+
  private:
   void ConfirmCommand();
 
   Command* m_currentCommand = nullptr;
   bool m_currentCommandChanged = true;
   Command* m_defaultCommand = nullptr;
-  std::string m_name;
   bool m_initializedDefaultCommand = false;
 
  public:
-  std::string GetName() const override;
-  void InitTable(std::shared_ptr<nt::NetworkTable> subtable) override;
-  std::string GetSmartDashboardType() const override;
-
- protected:
-  nt::NetworkTableEntry m_hasDefaultEntry;
-  nt::NetworkTableEntry m_defaultEntry;
-  nt::NetworkTableEntry m_hasCommandEntry;
-  nt::NetworkTableEntry m_commandEntry;
+  void InitSendable(SendableBuilder& builder) override;
 };
 
 }  // namespace frc