feat(json properties): implement json properties

-- implement .prop() method for fetching json properties
-- implement .value() , .numberValue() and .boolValue() for fetching
properties value
-- implement .elements() for a list of elements in json array
-- implement .fieldNames() for a list of names for child nodes of the
current node (a property is also a child node)
-- add tests for all new implemented functions
-- update documentation with new methods
-- extend example_json for more possible combinations of object and list types
-- extend example_json for boolean and float values

Realted to #CAM-2458