Update basemapper to better support drone data TMS (zoom >19)

[spwoodcock]

Describe the bug

Metadata comparison

• Metadata from QGIS-generated mbtiles includes zoom levels:

• Compared to output from osm_fieldwork.basemapper:

Is the type=overlay vs type=baselayer relevant?

Tile data comparison

• osm-fieldwork generates the tile table with mixed png / jpg data.
• There are also some rows with missing data.

• QGIS generates consistent image format, depending on what is specified.
• There are no rows with missing data.

Image comparison

• The quality of the embedded images is the same between QGIS and osm-fieldwork.
• The correct data is inserted in the right place:

Possible solutions

• Add the zoom levels to metadata (this is likely the fix, used by display software)
• Add image conversion jpg --> png and vice versa.
• Do not append rows with empty data.