[datalogtool] Add datalogtool

This is a support tool for datalog file conversion (and eventually
download/remote datalog file management).

datalogtool/src/main/native/cpp/App.h

@@ -0,0 +1,11 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#pragma once
+
+#include <imgui.h>
+
+void SetNextWindowPos(const ImVec2& pos, ImGuiCond cond = 0,
+                      const ImVec2& pivot = ImVec2(0, 0));
+void SetNextWindowSize(const ImVec2& size, ImGuiCond cond = 0);