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/cpp/frc2/command/CommandBase.cpp

@@ -0,0 +1,62 @@
+/*----------------------------------------------------------------------------*/
+/* 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.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#include "frc2/command/CommandBase.h"
+
+#include <frc/smartdashboard/SendableBuilder.h>
+#include <frc/smartdashboard/SendableRegistry.h>
+#include <frc2/command/CommandScheduler.h>
+#include <frc2/command/SetUtilities.h>
+
+using namespace frc2;
+
+CommandBase::CommandBase() {
+  frc::SendableRegistry::GetInstance().AddLW(this, GetTypeName(*this));
+}
+
+void CommandBase::AddRequirements(
+    std::initializer_list<Subsystem*> requirements) {
+  m_requirements.insert(requirements.begin(), requirements.end());
+}
+
+void CommandBase::AddRequirements(wpi::SmallSet<Subsystem*, 4> requirements) {
+  m_requirements.insert(requirements.begin(), requirements.end());
+}
+
+wpi::SmallSet<Subsystem*, 4> CommandBase::GetRequirements() const {
+  return m_requirements;
+}
+
+void CommandBase::SetName(const wpi::Twine& name) {
+  frc::SendableRegistry::GetInstance().SetName(this, name);
+}
+
+std::string CommandBase::GetName() const {
+  return frc::SendableRegistry::GetInstance().GetName(this);
+}
+
+std::string CommandBase::GetSubsystem() const {
+  return frc::SendableRegistry::GetInstance().GetSubsystem(this);
+}
+
+void CommandBase::SetSubsystem(const wpi::Twine& subsystem) {
+  frc::SendableRegistry::GetInstance().SetSubsystem(this, subsystem);
+}
+
+void CommandBase::InitSendable(frc::SendableBuilder& builder) {
+  builder.SetSmartDashboardType("Command");
+  builder.AddStringProperty(".name", [this] { return GetName(); }, nullptr);
+  builder.AddBooleanProperty("running", [this] { return IsScheduled(); },
+                             [this](bool value) {
+                               bool isScheduled = IsScheduled();
+                               if (value && !isScheduled) {
+                                 Schedule();
+                               } else if (!value && isScheduled) {
+                                 Cancel();
+                               }
+                             });
+}