Clarify default DB path in nilmdb_server.py help text

nilmdb/scripts/nilmdb_server.py

@@ -22,7 +22,7 @@ def main():
     group.add_argument('-p', '--port', help = 'Listen on the given port',
                        type = int, default = 12380)
     group.add_argument('-d', '--database', help = 'Database directory',
-                       default = os.path.join(os.getcwd(), "db"))
+                       default = "./db")
     group.add_argument('-q', '--quiet', help = 'Silence output',
                        action = 'store_true')
     group.add_argument('-t', '--traceback',