Implement scrolling with group

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitCardListView.kt

@@ -63,8 +63,13 @@ class HabitCardListView(
         set(value) {
             field = value
             attachedHolders
-                .map { it.itemView as HabitCardView }
-                .forEach { it.dataOffset = value }
+                .forEach {
+                    if (it.itemView is HabitCardView) {
+                        (it.itemView as HabitCardView).dataOffset = value
+                    } else {
+                        (it.itemView as HabitGroupCardView).dataOffset = value
+                    }
+                }
         }
 
     private val attachedHolders = mutableListOf<HabitCardViewHolder>()

uhabits-android/src/main/java/org/isoron/uhabits/activities/habits/list/views/HabitGroupCardView.kt

@@ -30,6 +30,8 @@ class HabitGroupCardView(
 ) : FrameLayout(context),
     ModelObservable.Listener {
 
+    var dataOffset = 0
+
     var habitGroup: HabitGroup? = null
         set(newHabitGroup) {
             if (isAttachedToWindow) {