adds sphere_radius parameter to spmap interpolation method

doc/src/interp_methods.dox

input/couple_config_test.yaml

python/yac.pyx

src/core/interp_method_spmap.c

src/core/interp_method_spmap.h

src/core/interp_stack_config.c

src/core/interp_stack_config.h

src/core/yac_core.F90

src/mci/config_yaml.c

src/mci/yac.c

src/mci/yac.h

src/mci/yac_global.F90

src/mci/yac_module.F90

tests/core/test_fortran_api.F90

tests/core/test_interp_method_spmap_parallel.c

tests/core/test_interp_stack_config.c

tests/mci/test_couple_config.c

tests/mci/test_dynamic_config.F90

tests/mci/test_dynamic_config_c.c

tests/python/test_interface.py