Version MK IV - released with CCP4 7.1

Replacement of openMP with std::async
Generation of WURCS string and cross-validation with GlyTouCan and GlyConnect
Closest match detection in GlyConnect
Minor bug fixes from MKIII, adoption of carbohydrate remediation standards.
Replaced nlohmann::json with sajson, that should hopefully now let Privateer MKIV build on MacOS 10.9 Mavericks.