Updates all Entity models to use SetPropertyValueAndDetectChanges for setting all simple properties so that

tracking changes works the way it is supposed to. Creates a TracksChangesEntityBase class for any other entity
that wants to implement IRememberBeingDirty (now Entity inherits from this). Upgraded a bunch of other entities that
were not tracking changes properly.

src/Umbraco.Core/Models/DictionaryItem.cs

@@ -42,8 +42,11 @@ namespace Umbraco.Core.Models
             get { return _parentId; }
             set
             {
-                _parentId = value;
-                OnPropertyChanged(ParentIdSelector);
+                SetPropertyValueAndDetectChanges(o =>
+                {
+                    _parentId = value;
+                    return _parentId;
+                }, _parentId, ParentIdSelector);
             }
         }
 
@@ -56,8 +59,11 @@ namespace Umbraco.Core.Models
             get { return _itemKey; }
             set
             {
-                _itemKey = value;
-                OnPropertyChanged(ItemKeySelector);
+                SetPropertyValueAndDetectChanges(o =>
+                {
+                    _itemKey = value;
+                    return _itemKey;
+                }, _itemKey, ItemKeySelector);
             }
         }
 
@@ -70,8 +76,11 @@ namespace Umbraco.Core.Models
             get { return _translations; }
             set
             {
-                _translations = value;
-                OnPropertyChanged(TranslationsSelector);
+                SetPropertyValueAndDetectChanges(o =>
+                {
+                    _translations = value;
+                    return _translations;
+                }, _translations, TranslationsSelector);
             }
         }