Done:
Algorithm for tiles with change in resolution between North/South edge
of tiles. No change of resolution taken into account between West/East
edge of tiles as known DEM does not have such change.
Algorithm done also for corner zipper tiles.
Test with dummy SRTM
To be done:
Test with real data from SRTM

Algorithm to be defined for DEM tiles without the same resolution.
Done:
Test on anti-meridian added
Test with real data from SRTM (put in comment as needs GDAL)

Algorithm to be defined for DEM tiles without the same resolution.
Some tests around anti-meridian need to be added.
Some tests with more real data to be added.

Change http to https

Fixes #391

Fixes #391

Fixes #390

Fixes #388