Revert "Issue #13 - Pathoverlay does not work with 512x512 tiles."

This reverts commit 7b19c5db3e6f2359d599af5e61ccf523fa9a8031.
Issue #81. Get rid of constant MAXIMUM_ZOOMLEVEL And instead use a calculated maximum zoom level based on tile size.
Issue #81. Scale tiles according to screen dpi. We do this by adjusting the tile size of the tile source relative to the dpi density.
Make sure we set the scaled tile size through the constructor too.
Make tile density scaling optional and disabled by default.
Merge branch 'fix_dpi_scaling'