Changed removeFile() to use xbmcvfs instead of regular file access
Updated the RemoveDirectory() function to use xbmcvfs.

Created the RemoveDirectoryRecursivelly() because I could not find any equivalent to shutil.rmtree(dir) in xbmcvfs. In order to support the progress bar in the dialog, I've also created a countFilesAndDirs() function to be able to calculate the percentage completed.