Add finger gateway

This adds the zuul-fingergw app that should be run as root (so that
it can connect to the standard finger port 79), but changes user privs
immediately after binding that port.

Common streaming functions have been moved to streamer_utils.py to
be shared among modules.

Support for CommandSocket has been included.

Change-Id: Ia35492fe951e7b9367eeab0b145d96189d72c364
diff --git a/setup.cfg b/setup.cfg
index 63ff562..dea3158 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -28,6 +28,7 @@
     zuul-bwrap = zuul.driver.bubblewrap:main
     zuul-web = zuul.cmd.web:main
     zuul-migrate = zuul.cmd.migrate:main
+    zuul-fingergw = zuul.cmd.fingergw:main
 
 [build_sphinx]
 source-dir = doc/source