doc: initial RapidCheck property-based testing documentation
doc: initial RapidCheck property-based testing documentation

Former-commit-id: a3cffb92fa320501a8262380282d91d5be2cf2d9
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin