feat(editor): heightmap terrain from the terrain model of GUGiK, fitted to the tracks of the scenery

- editorNmt: squares of 500 m of the NMT at 1 m from the WCS service of geoportal.gov.pl, as GeoTIFF, fetched in the
  background, kept in editor/cache/nmt and sampled in the coordinates of the scenery, placed as its orthophoto is
- the terrain panel's Terrain model section: Fit to the tracks moves the model up or down by the median of the
  differences to the formation of the tracks (Biała Podlaska, built at 0: -145.73 m, 0.28 m around it); Along the tracks
  and Around the camera make the chunks as the model comes in; each path gets its formation and slopes 1:1.5 as a modifier
  of the terrain, laid over each other into one corridor, bridges and tunnels keep the model; the orthophoto is turned
  on and laid onto the new ground
- the http client of the orthophoto in editorHttp, shared; fill_from_nearest in editormodeshared.h
- after the generator of Hirek (MaszynaTerrainGenerator): the WCS requests, the cache of squares, the corridor by envelopes
- self-tests nmtfit, nmtmake, nmtwait

editor/editorHttp.hpp

@@ -0,0 +1,44 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <cstdint>
+#include <functional>
+#include <memory>
+#include <string>
+#include <vector>
+
+// a minimal blocking https GET for the services the editor fetches its aids from (orthophoto, terrain model)
+namespace editor_http
+{
+
+// true to give the transfer up
+using stop_check = std::function<bool()>;
+
+// one instance per worker thread
+class client
+{
+  public:
+	client();
+	~client();
+	client(client const &) = delete;
+	client &operator=(client const &) = delete;
+
+	bool get(std::string const &Url, std::vector<std::uint8_t> &Out, std::string &Error, stop_check const &Stop);
+
+  private:
+	struct platform;
+	std::unique_ptr<platform> m_platform;
+};
+
+// whether this build can fetch anything
+bool available();
+
+} // namespace editor_http