Add method to MuranoPL that would allow to make object clone

For scaling scenarios it is very useful to be able to specify object (subset of object model) that can be used as a master copy for clones that are created on demand. It is necessary to have clone() function that will create deep copy of the object - will create another set of objects with the same input properties but with different IDs. Referenced classes that are not belong to cloned object should not be cloned but a reference to the same object be used instead