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/cpp/SmartDashboard/SendableBase.cpp

@@ -0,0 +1,91 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "SmartDashboard/SendableBase.h"
+
+#include "LiveWindow/LiveWindow.h"
+
+using namespace frc;
+
+/**
+ * Creates an instance of the sensor base.
+ *
+ * @param addLiveWindow if true, add this Sendable to LiveWindow
+ */
+SendableBase::SendableBase(bool addLiveWindow) {
+  if (addLiveWindow) LiveWindow::GetInstance()->Add(this);
+}
+
+/**
+ * Free the resources used by this object.
+ */
+SendableBase::~SendableBase() { LiveWindow::GetInstance()->Remove(this); }
+
+std::string SendableBase::GetName() const {
+  std::lock_guard<wpi::mutex> lock(m_mutex);
+  return m_name;
+}
+
+void SendableBase::SetName(const llvm::Twine& name) {
+  std::lock_guard<wpi::mutex> lock(m_mutex);
+  m_name = name.str();
+}
+
+std::string SendableBase::GetSubsystem() const {
+  std::lock_guard<wpi::mutex> lock(m_mutex);
+  return m_subsystem;
+}
+
+void SendableBase::SetSubsystem(const llvm::Twine& subsystem) {
+  std::lock_guard<wpi::mutex> lock(m_mutex);
+  m_subsystem = subsystem.str();
+}
+
+/**
+ * Add a child component.
+ *
+ * @param child child component
+ */
+void SendableBase::AddChild(std::shared_ptr<Sendable> child) {
+  LiveWindow::GetInstance()->AddChild(this, child);
+}
+
+/**
+ * Add a child component.
+ *
+ * @param child child component
+ */
+void SendableBase::AddChild(void* child) {
+  LiveWindow::GetInstance()->AddChild(this, child);
+}
+
+/**
+ * Sets the name of the sensor with a channel number.
+ *
+ * @param moduleType A string that defines the module name in the label for the
+ *                   value
+ * @param channel    The channel number the device is plugged into
+ */
+void SendableBase::SetName(const llvm::Twine& moduleType, int channel) {
+  SetName(moduleType + llvm::Twine('[') + llvm::Twine(channel) +
+          llvm::Twine(']'));
+}
+
+/**
+ * Sets the name of the sensor with a module and channel number.
+ *
+ * @param moduleType   A string that defines the module name in the label for
+ *                     the value
+ * @param moduleNumber The number of the particular module type
+ * @param channel      The channel number the device is plugged into (usually
+ * PWM)
+ */
+void SendableBase::SetName(const llvm::Twine& moduleType, int moduleNumber,
+                           int channel) {
+  SetName(moduleType + llvm::Twine('[') + llvm::Twine(moduleNumber) +
+          llvm::Twine(',') + llvm::Twine(channel) + llvm::Twine(']'));
+}