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/SetUtilities.h

@@ -0,0 +1,29 @@
+/*----------------------------------------------------------------------------*/
+/* 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
+
+#include <wpi/ArrayRef.h>
+#include <wpi/SmallVector.h>
+
+namespace frc2 {
+template <typename T>
+void SetInsert(wpi::SmallVectorImpl<T*>& vector, wpi::ArrayRef<T*> toAdd) {
+  for (auto addCommand : toAdd) {
+    bool exists = false;
+    for (auto existingCommand : vector) {
+      if (addCommand == existingCommand) {
+        exists = true;
+        break;
+      }
+    }
+    if (!exists) {
+      vector.emplace_back(addCommand);
+    }
+  }
+}
+}  // namespace frc2