Don't print messages to the console without a plugin prefix.

It's bad practice.

ProtocolLib/src/main/java/com/comphenix/protocol/ProtocolLibrary.java

@@ -117,7 +117,7 @@ public class ProtocolLibrary extends JavaPlugin {
 				public void onPacketReceiving(PacketEvent event) {
 					Object handle = event.getPacket().getHandle();
 					
-					System.out.println(String.format(
+					logger.info(String.format(
 							"RECEIVING %s@%s from %s.",
 							handle.getClass().getSimpleName(), handle.hashCode(), event.getPlayer().getName()
 					));
@@ -126,7 +126,7 @@ public class ProtocolLibrary extends JavaPlugin {
 				public void onPacketSending(PacketEvent event) {
 					Object handle = event.getPacket().getHandle();
 					
-					System.out.println(String.format(
+					logger.info(String.format(
 							"SENDING %s@%s from %s.",
 							handle.getClass().getSimpleName(), handle.hashCode(), event.getPlayer().getName()
 					));

ProtocolLib/src/main/java/com/comphenix/protocol/async/PacketSendingQueue.java

@@ -205,7 +205,7 @@ class PacketSendingQueue {
 		
 		} catch (PlayerLoggedOutException e) {
 			System.out.println(String.format(
-					"Warning: Dropped packet index %s of ID %s",
+					"[ProtocolLib] Warning: Dropped packet index %s of ID %s",
 					marker.getOriginalSendingIndex(), event.getPacketID()
 			));
 			

ProtocolLib/src/main/java/com/comphenix/protocol/injector/player/PlayerInjectionHandler.java

@@ -198,7 +198,7 @@ public class PlayerInjectionHandler {
 			if (injector != null) {
 				return injector.getPlayer();
 			} else {
-				System.out.println("Unable to find stream: " + inputStream);
+				logger.warning("Unable to find stream: " + inputStream);
 				return null;
 			}