Since commit 5a13c494 when I'm in a new area of the world that hasn't
yet been generated the debug log gets flooded with the following error:

Map::setNode(): Not allowing to place CONTENT_IGNORE while trying to
replace "default:dirt_with_grass" at (729,1,-219) (block (45,0,-14))

This commit fixes that.

Switch the license to be LGPLv2/later, with small parts still remaining as GPLv2/later, by agreement of major contributors