Sorted dict 1

Pull request for SortedDict and BalancedTree23 taking into account Kevin Squire's feedback from the past 12 days.
Stylistic suggestion: I would focus on the general overview of the containers first, rather than delving into the details of comparison functions, which I would put in its own section at or near the end.

In a first reading, most users will just want to use the DataStructure, and while comparison definitions are important, it's quite likely that the initial pass for many/most users will be to use the container for simple types (strings, numbers, etc.), for which these things are already defined.