Optimization to Digital Miner search thread

This is a slight change to the digital miner search thread to remove the
object creation that occurs for each block checked. It is a sort of
minor thing, but it will help to keep the memory requirements for the
thread down and execution maybe slightly faster.
Fix additional source of Digital Miner tile entity freezing

The function nextSetBit was incorrectly assumed to search for indexes
starting after the index given, but it in fact is inclusive with the
index given, this can lead to the while loop turning infinite if a block
it is expecting to be there isn't there.
Remove blocks that are outside of loaded chunks from bitset list

Remove another potential source of unneeded calculations, if a digital
miner is chunkloaded and chunks it is considering are outside of loaded
chunks, they will be iterated through for each block mined.
Merge pull request #1066 from JDGBOLT/development

Digital Miner additional Fixes