More lenient loading of block entities

[pishleback]

I found the plot crashing when //loading schematics I'd saved on ORE and downloaded via schemati. I've made the loading of the block entity nbt data more lenient so that it more leniently handles the format used in the schematic I was trying to load. It was failing before this edit because the field was called count rather than Count and the type was Int rather than Byte. I've made a similar change too for the Slot field, though it was not that field causing me problems.