Cells are only ever using precise for storing their items, thus there is
no need for a sorted collection with in general logarithmic time.
Storing them inside a HashMap for constant time is a way better solution.
Also adds an UnsortedItemList without fuzzy handling.
If anyone tries to use it, it will currently throw an
UnsupportedOperationException, Should the need arise guava Collections2
could provide a filter for it, but it is no alternative with heavy usage
of fuzzy access.
Also some code cleanup, reducing the visibility when not needed as
protected/default as well as removing actually unused methods.
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