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/Spark.cpp

@@ -9,8 +9,6 @@
 
 #include <HAL/HAL.h>
 
-#include "LiveWindow/LiveWindow.h"
-
 using namespace frc;
 
 /**
@@ -41,5 +39,5 @@ Spark::Spark(int channel) : PWMSpeedController(channel) {
   SetZeroLatch();
 
   HAL_Report(HALUsageReporting::kResourceType_RevSPARK, GetChannel());
-  LiveWindow::GetInstance()->AddActuator("Spark", GetChannel(), this);
+  SetName("Spark", GetChannel());
 }