* CachingFileStorage: Added more callbacks to provide user with more information what's going on

* Changed TestCacheSupervisor for easier use of the many callbacks
* Adapted tests for new callbacks

* GroupBaseActivity: Added sync menu command
* Preferences: Added option to enable/disable offline caching
* App: don't lock database when user wants to reload. This is done in PasswordActivity and should be done there after the password was filled into the pw field
* CheckDatabaseForChanges.cs: used when syncing a non-cached database

src/Kp2aUnitTests/TestKp2aApp.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using Android.App;
 using Android.Content;
 using Android.OS;
@@ -29,6 +30,18 @@ namespace Kp2aUnitTests
 			
 		}
 
+		public void LockDatabase(bool allowQuickUnlock = true)
+		{
+			throw new NotImplementedException();
+		}
+
+		public void LoadDatabase(IOConnectionInfo ioConnectionInfo, MemoryStream memoryStream, string password, string keyFile,
+		                         ProgressDialogStatusLogger statusLogger)
+		{
+			_db.LoadData(this, ioConnectionInfo, memoryStream, password, keyFile, statusLogger);
+			
+		}
+
 		public Database GetDb()
 		{
 			return _db;