"Riverflow map generator" updated: v1.1.1

Register mapgen function in 1st place

Use biomegen.skip_chunk when skipping air chunk

Print grid generation time

Add player spawner and override core.get_spawn_level

Minor fixup

Use new API and new structure of mapgen_rivers settings

Fix spawnplayer by loading grid on request

Remove load_all in settingtypes.txt

Re-organize settingtypes.txt

Update README, mod.conf, and add .cdb.json. Bump version to 1.1.1.