Adds operations for circular linked list (#1584)

* Adds, append, len, print operations for circular linked list

* Adds, prepend support

* Adds, delete from front of the list

* Adds, delete_rear support

* Adds, method documentations

* Adds, type checking and doctests

* Updates doctest for delete ops

* Addressing requested changes

* Removes unused import

* Fixes failing doctests

* Minor modifications...