It'd take years to figure out what caused the accident.

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

- Node placement code moved to Lua
- Mineral system removed (added default:stone_with_coal and default:stone_with_iron).
- MapBlock and MapNode serialization updated.
- Mapgen: Frequency of iron increased.
- node_dig callback and related changes.

Fixed the problem of <=r548 clients fucking up maps on >=r549 servers. Also, already fucked up maps are now loaded correctly.

Moved some mapnode content stuff from mapnode.{h,cpp} and digging property stuff from material.cpp to content_mapnode.{h,cpp}