Breaking Changes:

* Removed JumboFixedItemInv, as all of the optimisations that would have bee added to it will instead be added to SimpleFixedItemInv.

Changes:

* Updated to minecraft 1.14.1 Pre-Release 2
* Added ItemInsertable.getPureInsertable(), which returns an object that *only* implements ItemInsertable
* Added ItemExtractable.getPureExtractable(), which returns an object that *only* implements ItemInsertable
* Added ItemEntityAttributeUtil.getSpecialExtractable(Entity) which can return an IntemExtractable from item entities.
* Added ExactItemFilter, which is similar to an ExactItemStackFilter but only filters on Item's rather than the whole ItemStack.
* Made SimpleFixed{Item/Fluid}Inv implement {Item/Fluid}Transferable.

Bug Fixes:

* Fixed voxel-bounded attribute searches not respecting the bounds of contained attributes.
* Fixed the collections returned by ItemStackCollections sometimes not working properly. (And by sometimes I think it was "whenever you used them")
