Started to work on new block hiding feature, simple BlockMask impl.
Fixed BlockMask implementation and added naive impl to chunk.cpp/h.
Fixed small problem in chunk.cpp with getting the block data.
Put BlockMask object into a shared_ptr to prevent copying the big
block bitmask all the time.
Improved performance of block mask, made it a bit more intelligent.
Improved performance by not requesting the block data every time,
the block mask caches if all data values of a specific are hidden.

It should work, block mask test case is successful, but something
is still fishy...
Of course the block mask thingy can't properly work...
when the getBlockData doesn't have a force mode too.
Added method to use a bit mask when showing/hiding blocks to
show/hide multiple blocks,
Started to work on method to load block mask from string, very simple
yet, no validation
Some more comments on block mask, commented debug output.
Explicitly set default state of block mask to setAll(true).
Added a block_mask option and connected it to the block mask class.
*derp* Forgot the fake error message when parsing block mask.
WorldCrop::getBlockMask() returns a nullptr if there is no block mask.
Added an option to skip rendering unpopulated chunks.
Fixed directly calling operator bool(), didn't work with gcc-4.4.
issue #94
Accidentally didn't use boost compatibility code, used boost directlry.
Should fix #92 and #94.
Merge branch 'mapcrafter_library'

Conflicts:
	src/mapcraftercore/config/sections/world.cpp
Added small hint about new global section names.
Fix for issue with older boost filesystem versions.
#95
Improved error detection with invalid conversions in util::as<T>(...).
Started to document block mask format a bit.