Add implementation of ws_object_attr_type()
Add documentation to ws_object_attr_read()
Add ws_object_get_value_for_attr() method
Add stub for ws_object_get_value_for_attr()
Outsource attr-type-value-type map into static const
Add more information in attr-type-value-type map, including type size and init function
Add implementation for ws_object_get_value_for_attr()