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/Commands/PIDCommand.cpp

@@ -7,6 +7,8 @@
 
 #include "Commands/PIDCommand.h"
 
+#include "SmartDashboard/SendableBuilder.h"
+
 using namespace frc;
 
 PIDCommand::PIDCommand(const std::string& name, double p, double i, double d,
@@ -65,9 +67,8 @@ double PIDCommand::GetSetpoint() const { return m_controller->GetSetpoint(); }
 
 double PIDCommand::GetPosition() { return ReturnPIDInput(); }
 
-std::string PIDCommand::GetSmartDashboardType() const { return "PIDCommand"; }
-
-void PIDCommand::InitTable(std::shared_ptr<nt::NetworkTable> subtable) {
-  m_controller->InitTable(subtable);
-  Command::InitTable(subtable);
+void PIDCommand::InitSendable(SendableBuilder& builder) {
+  m_controller->InitSendable(builder);
+  Command::InitSendable(builder);
+  builder.SetSmartDashboardType("PIDCommand");
 }