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/Drive/DifferentialDrive.h

@@ -102,7 +102,7 @@ class DifferentialDrive : public RobotDriveBase {
   static constexpr double kDefaultQuickStopAlpha = 0.1;
 
   DifferentialDrive(SpeedController& leftMotor, SpeedController& rightMotor);
-  virtual ~DifferentialDrive() = default;
+  ~DifferentialDrive() override = default;
 
   DifferentialDrive(const DifferentialDrive&) = delete;
   DifferentialDrive& operator=(const DifferentialDrive&) = delete;
@@ -118,6 +118,8 @@ class DifferentialDrive : public RobotDriveBase {
   void StopMotor() override;
   void GetDescription(llvm::raw_ostream& desc) const override;
 
+  void InitSendable(SendableBuilder& builder) override;
+
  private:
   SpeedController& m_leftMotor;
   SpeedController& m_rightMotor;

wpilibc/src/main/native/include/Drive/KilloughDrive.h

@@ -55,7 +55,7 @@ class KilloughDrive : public RobotDriveBase {
   KilloughDrive(SpeedController& leftMotor, SpeedController& rightMotor,
                 SpeedController& backMotor, double leftMotorAngle,
                 double rightMotorAngle, double backMotorAngle);
-  virtual ~KilloughDrive() = default;
+  ~KilloughDrive() override = default;
 
   KilloughDrive(const KilloughDrive&) = delete;
   KilloughDrive& operator=(const KilloughDrive&) = delete;
@@ -67,6 +67,8 @@ class KilloughDrive : public RobotDriveBase {
   void StopMotor() override;
   void GetDescription(llvm::raw_ostream& desc) const override;
 
+  void InitSendable(SendableBuilder& builder) override;
+
  private:
   SpeedController& m_leftMotor;
   SpeedController& m_rightMotor;

wpilibc/src/main/native/include/Drive/MecanumDrive.h

@@ -67,7 +67,7 @@ class MecanumDrive : public RobotDriveBase {
   MecanumDrive(SpeedController& frontLeftMotor, SpeedController& rearLeftMotor,
                SpeedController& frontRightMotor,
                SpeedController& rearRightMotor);
-  virtual ~MecanumDrive() = default;
+  ~MecanumDrive() override = default;
 
   MecanumDrive(const MecanumDrive&) = delete;
   MecanumDrive& operator=(const MecanumDrive&) = delete;
@@ -79,6 +79,8 @@ class MecanumDrive : public RobotDriveBase {
   void StopMotor() override;
   void GetDescription(llvm::raw_ostream& desc) const override;
 
+  void InitSendable(SendableBuilder& builder) override;
+
  private:
   SpeedController& m_frontLeftMotor;
   SpeedController& m_rearLeftMotor;

wpilibc/src/main/native/include/Drive/RobotDriveBase.h

@@ -12,9 +12,9 @@
 #include <llvm/ArrayRef.h>
 #include <llvm/raw_ostream.h>
 
-#include "ErrorBase.h"
 #include "MotorSafety.h"
 #include "MotorSafetyHelper.h"
+#include "SmartDashboard/SendableBase.h"
 
 namespace frc {
 
@@ -23,7 +23,7 @@ class SpeedController;
 /**
  * Common base class for drive platforms.
  */
-class RobotDriveBase : public MotorSafety, public ErrorBase {
+class RobotDriveBase : public MotorSafety, public SendableBase {
  public:
   /**
    * The location of a motor on the robot for the purpose of driving.
@@ -39,7 +39,7 @@ class RobotDriveBase : public MotorSafety, public ErrorBase {
   };
 
   RobotDriveBase();
-  virtual ~RobotDriveBase() = default;
+  ~RobotDriveBase() override = default;
 
   RobotDriveBase(const RobotDriveBase&) = delete;
   RobotDriveBase& operator=(const RobotDriveBase&) = delete;