Change default ports and add clearer default to gamedir template, as per #1365.

Dockerfile

@@ -5,7 +5,7 @@
 # on DockerHub, which can be used as the basis for creating
 # an Evennia game within a container. This base image can be
 # found in DockerHub at https://hub.docker.com/r/evennia/evennia/
-# 
+#
 # For more information on using it to build a container to run your game, see
 #
 # https://github.com/evennia/evennia/wiki/Running%20Evennia%20in%20Docker
@@ -26,7 +26,7 @@ RUN pip install -e /usr/src/evennia
 ONBUILD ADD . /usr/src/game
 
 # make the game source hierarchy persistent with a named volume.
-# during development this is typically superceded by directives in 
+# during development this is typically superceded by directives in
 # docker-compose.yml or the CLI to mount a local directory.
 VOLUME /usr/src/game
 
@@ -36,5 +36,5 @@ WORKDIR /usr/src/game
 # startup command
 CMD ["evennia", "-i", "start"]
 
-# expose the default ports
-EXPOSE 8000 8001 4000
+# expose the telnet, webserver and websocket client ports
+EXPOSE 4000 4001 4005