Default min level for block submissions increased to 3

This doesn't affect minting rewards; it is simply a means of reducing block candidates. There should be no noticeable difference other than hopefully less re-orgs. We can ultimately do a hard fork and increase Blockchain.minAccountLevelToMint but this allows us to test the approach in a lower risk way.

src/main/java/org/qortal/controller/BlockMinter.java

@@ -16,6 +16,7 @@ import org.qortal.account.PrivateKeyAccount;
 import org.qortal.block.Block;
 import org.qortal.block.Block.ValidationResult;
 import org.qortal.block.BlockChain;
+import org.qortal.data.account.AccountData;
 import org.qortal.data.account.MintingAccountData;
 import org.qortal.data.account.RewardShareData;
 import org.qortal.data.block.BlockData;
@@ -47,6 +48,11 @@ public class BlockMinter extends Thread {
 	// Recovery
 	public static final long INVALID_BLOCK_RECOVERY_TIMEOUT = 10 * 60 * 1000L; // ms
 
+	// Min account level to submit blocks
+	// This is an unvalidated version of Blockchain.minAccountLevelToMint
+	// and exists only to reduce block candidates by default.
+	private static int MIN_LEVEL_FOR_BLOCK_SUBMISSION = 3;
+
 	// Constructors
 
 	public BlockMinter() {
@@ -130,6 +136,16 @@ public class BlockMinter extends Thread {
 						madi.remove();
 						continue;
 					}
+
+					// Optional (non-validated) prevention of block submissions below a defined level
+					AccountData accountData = repository.getAccountRepository().getAccount(mintingAccount.getAddress());
+					if (accountData != null) {
+						Integer level = accountData.getLevel();
+						if (level != null && level < MIN_LEVEL_FOR_BLOCK_SUBMISSION) {
+							madi.remove();
+							continue;
+						}
+					}
 				}
 
 				List<Peer> peers = Network.getInstance().getHandshakedPeers();