Testing and corrections on sorting.  Time to move on!

 - Fixed rule limit validation  not detecting hotbar spaces properly
 - ~~Fixed lack of null/overlap checking which caused sort to fail~~
 - Changed `isToolType` to `getToolType`, also added correction for shovel and spade, used that method in the sorting engine too (wohoo, no more exceptions as control statements)
 - Added default groups to `ItemGroupExists`
 - Addressed case sensitivity in the original `MatchesMaterial` method
 - Fixed error when applying a double chest rule to a double chest, mistakenly warning that it's a single chest
 - Added separate method to retrieve new indices, integrating the null check from above
 - Fixed null check when assigning item stacks to claimed indices in last resort
 - Added durability comparison in the `Comparators` superclass