unused attributes can be displayed vertically via 'unusedAttrsVertical: true' option
unused attributes can be auto-sorted alphabetically via 'autoSortUnusedAttrs: true' option
Revert "unused attributes can be auto-sorted alphabetically via 'autoSortUnusedAttrs: true' option"

This reverts commit b6fbdf154471d1ec7f927148b277352cba8734bf.

the original author did not like it, see: https://github.com/nicolaskruchten/pivottable/pull/80#issuecomment-29202007
placements fixed in vertically oriented unused attributes
"unused attributes can be auto-sorted alphabetically via 'autoSortUnusedAttrs: true' option" is flopped back

This reverts commit 3cff0ad1e22290df2f7b152348b256860c537a13.
natural sorting algorithm is extracted from PivotData class; and is also used in sorting unused attributes
compiling libs for changes from #80 for #67