Log entry max to 2k, remove logging in hot codepaths (#1459)

On a recent trip through a CPU profile taken while Signal Desktop
churned through a large backlog of messages, it was clear that
console.log was a major source of time spent, primarily the sort
operation required after every new entry is added to the Backbone
collection. So, three different techniques to combat this:

1) Reduce the maximum number of entries in the collection from 5k to 2k
2) No more logging of add/update/remove queue in MessageReceiver
3) No more log entries in Message.handleDataMessage main codepath

FREEBIE

js/debugLog.js

@@ -40,7 +40,7 @@
         }
     });
 
-    var MAX_MESSAGES = 5000;
+    var MAX_MESSAGES = 2000;
     var PHONE_REGEX = /\+\d{7,12}(\d{3})/g;
     var log = new DebugLog();
     if (window.console) {