Adds documentation on using iterators over lists
Adds documentation on using iterators over lists

This solves a TODO in the code, refs #2277

tbrowder/doc,jonathanstowe/doc,jonathanstowe/doc,stmuk/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc,MasterDuke17/doc,tbrowder/doc,stmuk/doc,stmuk/doc,jonathanstowe/doc,perl6/doc,perl6/doc,perl6/doc,stmuk/doc,jonathanstowe/doc,perl6/doc,MasterDuke17/doc,perl6/doc,MasterDuke17/doc,jonathanstowe/doc,stmuk/doc