added sfm- prefix to streamsample log file names
Updated file_path in delete_conf_file to reflect new location for conf files in /supervisor-sfm-conf and new settings variable SFM_LOCATION
Rewrote TwitterFilter clean() validation logic (and wording): no validation if is_active==False; else: check for username conflicts with 1) TWITTER_DEFAULT_USERNAME (used for streamsample) and 2) any other active filters. Fixes #130 first requirement bullet.
Simplified logic for updating (deleting+recreating) existing filterstream conf file; added console output; added comments; Updated help text; updated manage.py location relative to SFM_LOCATION; changed variable name from filtered to tfilter; removed extraneous /bin from env path; updated log file path, names; eliminated use of FILEPATH (in favor of SFM_LOCATION).