RangeController

-   This renames ContentController, nee ArrayController, to RangeController and
    expands the scope and correctness of the implementation.

-   RangeController now has methods that proxy the underlying collection for
    the purpose of proactively managing the selection.

-   RangeController now supports a complete pipeline from "content" to
    "organizedContent" (previously "visibleContent"), through "sortPath",
    "reversed", "filterPath", "visibleIndexes", "start", and "length".

-   RangeController now has proxy methods "select", "deselect",
    "clearSelection" to more gracefully handle the "avoidsEmptySelection" and
    "multiSelect" flags.

-   RangeController is fully JSDoc-ed.  All instance properties are annotated
    on the prototype.  Judgement calls have been made about whether properies
    are private-by-underscore and private-by-jsdoc.

-   "object" properties of iterations exist but are deprecated in favor of
    "content".