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.

The huge item definition and item namespace unification patch (itemdef), see http://c55.me/minetest/wiki/doku.php?id=changes:itemdef

Make Connection::Receive return the data via a SharedBuffer reference, so the caller doesn't have to choose the right buffer size in advance.

Conflicts:

	src/test.cpp

Add new Connection test in test.cpp in case needed in the future (commented out), improve comments in test.cpp a bit

Use the logger; also, default to not showing much crap in console. Use --info-on-stderr to enable crap.

New map generator added (and SQLite, messed up the commits at that time...) (import from temporary git repo)

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