[json-lib] updated documentation, added feature list
[json-lib] updated documentation, added feature list

kohsuke/Json-lib,flytreeleft/Json-lib,vladuke/json-lib-fork,flytreeleft/Json-lib,vladuke/json-lib-fork,flytreeleft/Json-lib,vladuke/json-lib-fork,aalmiray/Json-lib,kohsuke/Json-lib,aalmiray/Json-lib