Adding skeleton for a linked list implementation in Java.
Adding node constructors and some documentation.
Adding documentation for get.
Adding helper method for getting nodes at specific indices.
Adding documentation for the rest of the methods.
Added iterator for iterating over nodes.
Adding element iterator backed by node iterator.
Adding add and get implementations.

Tests should be added now, as there are obvious problems with the iterator.
These problems also apply to the get method.
Adding elements to the list should be done through the iterator,
but the iterator does not yet have an add implementation.