AddressMap features

* Define what the various accessibility bits mean for AddressMap

* Added address+size versions of read and write methods
Added more lower/upper methods for IntervalMap and IntervalSet
Changed "lower" and "upper" to "least" and "greatest"

Since these methods return end points, we should be using
superlative words rather than relative words. This is especially
important for methods like "lowerUnmapped(x)" whose return
value is related to an argument. In this case, "leastUnampped(x)"
makes it clear that some minimum limit is returned rather than any
value that is "lower" than "x".
Fixed Sawyer::Container::Map::Map