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/SmartDashboard/Sendable.h

@@ -7,27 +7,63 @@
 
 #pragma once
 
-#include <memory>
 #include <string>
 
-#include "networktables/NetworkTable.h"
+#include <llvm/Twine.h>
 
 namespace frc {
 
+class SendableBuilder;
+
 class Sendable {
  public:
-  /**
-   * Initializes a table for this sendable object.
-   *
-   * @param subtable The table to put the values in.
-   */
-  virtual void InitTable(std::shared_ptr<nt::NetworkTable> subtable) = 0;
+  virtual ~Sendable() = default;
 
   /**
-   * @return The string representation of the named data type that will be used
-   *         by the smart dashboard for this sendable
+   * Gets the name of this Sendable object.
+   *
+   * @return Name
    */
-  virtual std::string GetSmartDashboardType() const = 0;
+  virtual std::string GetName() const = 0;
+
+  /**
+   * Sets the name of this Sendable object.
+   *
+   * @param name name
+   */
+  virtual void SetName(const llvm::Twine& name) = 0;
+
+  /**
+   * Sets both the subsystem name and device name of this Sendable object.
+   *
+   * @param subsystem subsystem name
+   * @param name device name
+   */
+  void SetName(const llvm::Twine& subsystem, const llvm::Twine& name) {
+    SetSubsystem(subsystem);
+    SetName(name);
+  }
+
+  /**
+   * Gets the subsystem name of this Sendable object.
+   *
+   * @return Subsystem name
+   */
+  virtual std::string GetSubsystem() const = 0;
+
+  /**
+   * Sets the subsystem name of this Sendable object.
+   *
+   * @param subsystem subsystem name
+   */
+  virtual void SetSubsystem(const llvm::Twine& subsystem) = 0;
+
+  /**
+   * Initializes this Sendable object.
+   *
+   * @param builder sendable builder
+   */
+  virtual void InitSendable(SendableBuilder& builder) = 0;
 };
 
 }  // namespace frc