Corrected coordinate computation in drawing a sphere/disk. Now centering also working when box has negative origin.

# Conflicts:
#	.gitignore
#	install
#	openfpm_io
#	openfpm_numerics
#	src/CMakeLists.txt

# Conflicts:
#	.gitignore
#	install
#	openfpm_data
#	openfpm_io
#	openfpm_numerics
#	src/CMakeLists.txt

Fixed missing consideration of patches that may start / end within a group of nodes to which same pixel-value should be assigned, i.e. patches whose x-dim. is not a multiple of the refinement-factor in x.

Fixed considering patches that may start / end within a group of nodes to which same pixel-value should be assigned, i.e. patches whose x-dim. is not a multiple of the refinement-factor in x.