Extended and improved lists

Description

This MR extends and improves the linked lists in several ways:

• Split the linked list into a base class, with all the methods shared by all linked lists, and specialized lists that enforce that only variables of the correct type are inserted into the list.
• Lists can now store either copies or pointers to values.
• New has method to check if a given value is in the list.
• New method to copy a list.
• New delete method to delete an element from the list.
• New empty method to delete all elements from the list.

News snippet

Extended and improved lists.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.