Now Environment::clearAllObjects() unloads unused blocks in an interval
defined by max_clearobjects_extra_loaded_blocks (default 4096).

the following:
1. String concatenation in guiMainMenu.cpp - it is required for all
individual strings to be of the same type <unicode/non-unicode>; adding
explicit L qualifier before the other strings.
2. Correcting type of BlockMakeData to struct in place of class forward
declarations. This information is used for name decoration by Visual
Studio, leading to linker errors in case of mismatches.
3. Windows headers define max as a macro somewhere, leading to a compile
time error in profiler.h; using () around function to prevent macro match
from occurring.

- 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

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

Reduce EnvRef:set_node() time tenfold by postponing the dayNightDiff update until it is actually needed

- 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.

Collected and moved existing camera infrastructure from game.cpp to camera.cpp and camera.h. Introduced configuration settings 'fov' which chooses the camera's (vertical) field of view and 'view_bobbing' which currently does nothing. Other code refactored to not expect the FOV to be a build time constant.

Removed unused camera_position and camera_direction fields from Client. Moved ClientEnvironment::drawPostFx to ClientMap::renderPostFx -- this will make the camera management classes easier to write, as ClientMap already knows the camera position but ClientEnvironment doesn't and has to be told about it. This also eliminates the need for Client::getEnv(). Made the post effect color a content feature defined in content_mapnode.h.

* The map will reside in world/map.sqlite
* It will load from the sectors folder but will not save there

Fixed objects being sometimes not able to be stored statically in a block when block has been unloaded