feat(track): 3D sleepers and switch timbers, blade heel and throw from templates, one rail carving pass

- sleepers3d / sleepers3dplain / sleepers3dbed in eu07.ini: timbers put together from the begin, main and end parts of a model
  and stretched to their length, plain sleepers of their own model; tracks whose plain sleepers would touch are laid as one
  cluster, lines of timbers led by priority and turned to the bisectors of frogs and crossings at a limited rate, whole timbers
  under crossings, split ones between tracks with room to part them, gaps filled per rail and overlaps shortened or dropped;
  clusters worked out in a background thread while driving, on demand in the editor
- the ballast can be left out under the beams (sleepers3dbed no)
- blades get their heel and throw from the switch template or blades <heel> <throw> in the scenery; blades of double switches
  run on into the track linking them to the next switch
- rail cutting at frogs, wing rails, movable noses and switch crossings done by one carving pass (RailCarve)
- tint of the rail treads applied to the colour only, without the matte band at the frog
- a switch trailed through with a movable nose set the other way derails the vehicle
- self-tests: sleepercheck, sharedzones, beamsnear, throw, sleepersbg

rendering/geometrybank.h

@@ -138,6 +138,8 @@ public:
 	auto vertices( gfx::geometry_handle const &Geometry ) const -> gfx::vertex_array const &;
 	// provides direct access to vertex user data of specfied chunk
 	auto userdata( gfx::geometry_handle const &Geometry ) const -> gfx::userdata_array const &;
+	// kind of geometry of specified chunk, GL_TRIANGLES, GL_TRIANGLE_STRIP...
+	auto primitive( gfx::geometry_handle const &Geometry ) const -> unsigned int;
 
 protected:
 // types:
@@ -238,6 +240,8 @@ public:
 	auto vertices( gfx::geometry_handle const &Geometry ) const -> gfx::vertex_array const &;
 	// provides direct access to vertex data of specfied chunk
 	auto userdata( gfx::geometry_handle const &Geometry ) const -> gfx::userdata_array const &;
+	// kind of geometry of specified chunk
+	auto primitive( gfx::geometry_handle const &Geometry ) const -> unsigned int;
     // sets target texture unit for the texture data stream
     auto units() -> gfx::stream_units & { return m_units; }
     // provides access to primitives count