Spell storing fixes

* Fixed spell-storing magic item issue with '-ADD' and '-ANY' capabilities.
* Added  '-CHANGE' capability to spell-storing MIs.
* Added 'store' and 'lvl' attributes to MI data definitions to set the 'add', 'any' and 'change' status (defaults to 'none'), and to restrict the number of spell levels stored (defaults to 99).Extend
* handleAddAllPowers() to also deal with MU & PR spells at all levels, and made it asynchronous.
* Fixed checking valid spells & valid powers.
* Use stored spell row/column data to build item-specific spell lists.
* Ensure that --change-attr command rounds correctly for odd/even scores.