Made PFCoreManager automatically clear its staging directory (asyncronously) upon initialization of Parse.

Fixes half of #18.

Author: richardjrossiii

Parse/Internal/PFCoreManager.m

@@ -16,6 +16,7 @@
 #import "PFCurrentInstallationController.h"
 #import "PFCurrentUserController.h"
 #import "PFFileController.h"
+#import "PFFileManager.h"
 #import "PFInstallationController.h"
 #import "PFLocationManager.h"
 #import "PFMacros.h"
@@ -135,6 +136,9 @@ - (PFFileController *)fileController {
     dispatch_sync(_controllerAccessQueue, ^{
         if (!_fileController) {
             _fileController = [PFFileController controllerWithDataSource:self.dataSource];
+            // This is OK to do asynchronously here, as you can wait on the task being completed via
+            // PFMultiProcessFileLockController.
+            [PFFileManager removeDirectoryContentsAsyncAtPath:_fileController.stagedFilesDirectoryPath];
         }
         controller = _fileController;
     });