Also remove some unused parameters/functions

This commit refactors the majority of the Mapgen settings system.
- MapgenParams is now owned by MapSettingsManager, itself a part of ServerMap,
  instead of the EmergeManager.
- New Script API functions added:
    core.get_mapgen_setting
    core.get_mapgen_setting_noiseparams,
    core.set_mapgen_setting, and
    core.set_mapgen_setting_noiseparams.
- minetest.get/set_mapgen_params are deprecated by the above new functions.
- It is now possible to view and modify any arbitrary mapgen setting from a mod,
  rather than the base MapgenParams structure.
- MapgenSpecificParams has been removed.

Use this macro to disallow copying of an object using the assignment
operator or copy constructor.  This catches otherwise silent-but-deadly
mistakes such as "ServerMap map = env->getMap();" at compile time.

If so desired, it is still possible to copy a class, but it now requires
an explicit call to memcpy or std::copy.

Major refactor of emerge.cpp and Map::init/finishBlockMake

For usages of assert() that are meant to persist in Release builds (when NDEBUG is defined), replace those usages with persistent alternatives

* Also remove dead code Map::unloadUnusedData which is dead since a long time

Replace std::list by std::vector into ServerMap::listAllLoadableBlocks ServerMap::listAllLoadedBlocks and their database backends.
This adds a speedup on database migration and /clearobjects command

Also add a Lua API and chatcommand for this

Improve error handling in saveBlock()

MapgenParams is no longer a polymorphic class, eliminating the need for messy and bug-prone reallocations.
Separation between the common and mapgen-specific parameters is now strongly defined.
Mapgen parameters objects are now properly encapsulated within the proper subsystems.

The commit didn't work because the blocks weren't loaded yet.

This reverts commit 22dbbf0a.

Conflicts:
	minetest.conf.example

The real problem was that MapBlocks were not activated before getting sent to the client