Cleanup and bugfixes

- Remove not used code
- Fixed some code style
- use a subdirectory in the SDK caches folder, instead of creating another folder directly under caches
- Height of feedback cells only considers attachments that actually can be previewed.
- If an attachment has no source URL and no local URL, don't show it, not even a loading placeholder, don't consider to reserve space in the cell for it
- refresh attachment cache when new data is loaded or one or all message(s) with attachments have been deleted locally
- `feedbackObservationMode` is a property instead of a method

Classes/BITActivityIndicatorButton.m

@@ -1,10 +1,28 @@
-//
-//  BITActivityIndicatorButton.m
-//  HockeySDK
-//
-//  Created by Moritz Haarmann on 21.05.14.
-//
-//
+/*
+ * Copyright (c) 2012-2014 HockeyApp, Bit Stadium GmbH.
+ * All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person
+ * obtaining a copy of this software and associated documentation
+ * files (the "Software"), to deal in the Software without
+ * restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following
+ * conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+ * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
 
 #import "BITActivityIndicatorButton.h"