Fix wrong names.
Add docstrings to destructuring-bind & while-let.
Redefine `last' to return the car of the last cons. The original functionality lives as `cons-last'.
Make `last', `butlast' and `nbutlast' allow to be applied to sequence.
Redefine first, second ... tenth and rest. Now these functions can be applied to sequences.
Delete a TODO comment for `length'. `length' can be applied to sequences.