moving stan/math/boost_error_handling to stan/math/error_handling/boost_error_handling
renaming boost_error_handling.hpp to raise_domain_error.hpp
cleaning up raise_domain_error.hpp
splitting apart src/stan/math/error_handling.hpp
moving src/stan/math/functions/error_handling to src/stan/math/error_handling
moving check_finite out of stan/math/error_handling.hpp
moving check_greater out of stan/math/error_handling.hpp
moving check_greater_or_equal, check_less, check_less_or_equal out of stan/math/error_handling.hpp
moving check_bounded, check_nonnegative, check_positive out of stan/math/error_handling.hpp
moving check_consistent_size, check_consistent_sizes out of stan/math/error_handling.hpp