Improved vnf reader: downsized tiles, NB warnings cleanup

Closed username-removed-200434 requested to merge feature/ImprovedTileReading into develop

Changes in ReadVisNowField module:

  1. Added extende tile description low:up:step (low:up - extents of tile in original resolution, step - downsize step)
  2. Cleanup of NetBeans syntax warnings Added 2 binary datasets tatra_west_down.vnd and tatra_east_down.vnd and two vnf files as examples of tiled fields: tatra_2_sec.vnf and tatra_4_sec.vnf creating fields covering same area but with different resolutions