Also fixes long-standing accuracy issue due to unknown wider
object count not being incremented.

On the lua side, notably minetest.env:<function>(<args>) should now
be replaced by minetest.<function>(<args>).
The old way is and will stay supported for a long time.

Also:
Update and clean up lua_api.txt (by celeron55)
Move EnvRef to lua and remove add_rat and add_firefly (by kahrl)
Add separate src/util/CMakeLists.txt, other minor fixes (by kahrl)

- Neatly placed all emerge related code into a new file, emerge.cpp
- Greatly cleaned up the code in EmergeThread::Thread()
- Reworked Emerge queue.  Now an actual std::queue of v3s16 block positions
- Removed the completely unnecessary map of peer ids requesting blocks

Add ServerEnvironment::setNode()/removeNode() to allow setting nodes from the C++ side with proper script-defined initialization/destruction

No longer hide players who are dead. With models, a death animation should be used instead

Some changes requested by celeron55

Rename a lot of things in the code, and use better lua api function names

Minor code corrections

Bump protocol version up, since the models / animations / attachments code creates new client<->server messages

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

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