docker dev start: use the first sentence for shortdesc, not the second line

docker_dev_start.py

@@ -36,7 +36,7 @@
     program_build_date = str(__updated__)
     program_version_message = '%%(prog)s %s (%s)' % (
         program_version, program_build_date)
-    program_shortdesc = __doc__.split("\n")[1]
+    program_shortdesc = __doc__.split(".")[0]
     program_license = '''%s
 
   Created by Vincent Hatakeyama on %s.