Seems like etl and mapping diagrams have been neglected for a long time. Now it regenerates the files and places them in the source dir. This PR also fixes two broken files: * layers/aerodrome_label/mapping_diagram.png * layers/housenumber/mapping_diagram.png They were generated using the newest tools version with the fix https://github.com/openmaptiles/openmaptiles-tools/pull/65
waterway
Docs
Read the layer documentation at http://openmaptiles.org/schema#waterway

