Split the two command implementations into separate libraries (#2012)

This will allow us at the user code side to determine to include old commands, new commands or both.

wpilibNewCommands/src/main/native/include/frc2/command/CommandState.h

@@ -0,0 +1,33 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+namespace frc2 {
+/**
+ * Class that holds scheduling state for a command.  Used internally by the
+ * CommandScheduler
+ */
+class CommandState final {
+ public:
+  CommandState() = default;
+
+  explicit CommandState(bool interruptible);
+
+  bool IsInterruptible() const { return m_interruptible; }
+
+  // The time since this command was initialized.
+  double TimeSinceInitialized() const;
+
+ private:
+  double m_startTime = -1;
+  bool m_interruptible;
+
+  void StartTiming();
+  void StartRunning();
+};
+}  // namespace frc2