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/AnalogTrigger.cpp

@@ -25,6 +25,7 @@ using namespace frc;
 AnalogTrigger::AnalogTrigger(int channel)
     : AnalogTrigger(new AnalogInput(channel)) {
   m_ownsAnalog = true;
+  AddChild(m_analogInput);
 }
 
 /**
@@ -49,6 +50,7 @@ AnalogTrigger::AnalogTrigger(AnalogInput* input) {
   m_index = index;
 
   HAL_Report(HALUsageReporting::kResourceType_AnalogTrigger, input->m_channel);
+  SetName("AnalogTrigger", input->GetChannel());
 }
 
 AnalogTrigger::~AnalogTrigger() {
@@ -184,3 +186,7 @@ std::shared_ptr<AnalogTriggerOutput> AnalogTrigger::CreateOutput(
   return std::shared_ptr<AnalogTriggerOutput>(
       new AnalogTriggerOutput(*this, type), NullDeleter<AnalogTriggerOutput>());
 }
+
+void AnalogTrigger::InitSendable(SendableBuilder& builder) {
+  if (m_ownsAnalog) m_analogInput->InitSendable(builder);
+}