Adds JNI Simulator interface and updated Sim API (#1002)

The simulator was generated by https://github.com/ThadHouse/SimulatorGenerator

hal/src/test/native/cpp/Sim/AccelerometerSimTest.cpp

@@ -0,0 +1,42 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2018 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 "HAL/Accelerometer.h"
+#include "HAL/HAL.h"
+#include "Simulation/AccelerometerSim.h"
+#include "gtest/gtest.h"
+
+using namespace frc::sim;
+
+namespace hal {
+
+TEST(AcclerometerSimTests, TestActiveCallback) {
+  HAL_Initialize(500, 0);
+
+  AccelerometerSim sim{0};
+
+  sim.ResetData();
+
+  bool wasTriggered = false;
+  bool lastValue = false;
+
+  auto cb = sim.RegisterActiveCallback(
+      [&](wpi::StringRef name, const HAL_Value* value) {
+        wasTriggered = true;
+        lastValue = value->data.v_boolean;
+      },
+      false);
+
+  EXPECT_FALSE(wasTriggered);
+
+  HAL_SetAccelerometerActive(true);
+
+  EXPECT_TRUE(wasTriggered);
+  EXPECT_TRUE(lastValue);
+}
+
+}  // namespace hal