[command] Add NetworkButton (#2373)

Closes #2371

wpilibNewCommands/src/main/native/include/frc2/command/button/NetworkButton.h

@@ -0,0 +1,48 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2011-2020 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 <memory>
+
+#include <networktables/NetworkTable.h>
+#include <networktables/NetworkTableInstance.h>
+#include <wpi/Twine.h>
+
+#include "Button.h"
+
+namespace frc2 {
+/**
+ * A {@link Button} that uses a {@link NetworkTable} boolean field.
+ */
+class NetworkButton : public Button {
+ public:
+  /**
+   * Creates a NetworkButton that commands can be bound to.
+   *
+   * @param entry The entry that is the value.
+   */
+  explicit NetworkButton(nt::NetworkTableEntry entry);
+
+  /**
+   * Creates a NetworkButton that commands can be bound to.
+   *
+   * @param table The table where the networktable value is located.
+   * @param field The field that is the value.
+   */
+  NetworkButton(std::shared_ptr<nt::NetworkTable> table,
+                const wpi::Twine& field);
+
+  /**
+   * Creates a NetworkButton that commands can be bound to.
+   *
+   * @param table The table where the networktable value is located.
+   * @param field The field that is the value.
+   */
+  NetworkButton(const wpi::Twine& table, const wpi::Twine& field);
+};
+}  // namespace frc2