Use a Deque for roomEvents's ListModel

- Take a custom container callable for ListModel __init__ (defaults to
  list, must be a MutableSequence)

- Use a Deque for roomEvents, which is much faster for inserting
  new items at the beginning.

harmonyqml/components/chat/MessageDelegate.qml

@@ -7,7 +7,6 @@ Column {
     id: "rootCol"
 
     function mins_between(date1, date2) {
-        console.log(Math.round((((date2 - date1) % 86400000) % 3600000) / 60000))
         return Math.round((((date2 - date1) % 86400000) % 3600000) / 60000)
     }
 
@@ -59,8 +58,6 @@ Column {
         combine ? standardSpacing / 4 :
         standardSpacing
 
-    //Text { text: rootCol.topPadding }
-
     Daybreak { visible: dayBreak }
 
     MessageContent { visible: isMessage }