core, eth/filters, miner, xeth: Optimised log filtering

Log filtering is now using a MIPmap like approach where addresses of
logs are added to a mapped bloom bin. The current levels for the MIP are
in ranges of 1.000.000, 500.000, 100.000, 50.000, 1.000. Logs are
therefor filtered in batches of 1.000.

miner/worker.go

@@ -301,6 +301,8 @@ func (self *worker) wait() {
 					core.PutTransactions(self.chainDb, block, block.Transactions())
 					// store the receipts
 					core.PutReceipts(self.chainDb, work.receipts)
+					// Write map map bloom filters
+					core.WriteMipmapBloom(self.chainDb, block.NumberU64(), work.receipts)
 				}
 
 				// broadcast before waiting for validation