Added tasks to download and import media files form the server

* Added run_export_media task
* Added run_download_media task
* Added import_media task
* Added new setting MEDIA_DUMP_FILENAME to fabfile_settings.py.sample
* Fixed path of SERVER_MEDIA_BACKUP_DIR in fabfile_settings.py.sample
* Please update your fabfile_settings.py with those two fixes!
Released v0.8