Update docker file to better handle starting without an existing game folder

Dockerfile

@@ -7,7 +7,7 @@
 # Usage:
 #    cd to a folder where you want your game data to be (or where it already is).
 #
-#	docker run -it -p 4000:4000 -p 4001:4001 -p 4005:4005 -v $PWD:/usr/src/game evennia/evennia
+#	docker run -it --rm -p 4000:4000 -p 4001:4001 -p 4005:4005 -v $PWD:/usr/src/game evennia/evennia
 #
 #    (If your OS does not support $PWD, replace it with the full path to your current
 #    folder).
@@ -15,6 +15,14 @@
 #    You will end up in a shell where the `evennia` command is available. From here you
 #    can install and run the game normally. Use Ctrl-D to exit the evennia docker container.
 #
+#    You can also start evennia directly by passing arguments to the folder:
+#  
+#       docker run -it --rm -p 4000:4000 -p 4001:4001 -p 4005:4005 -v $PWD:/usr/src/game evennia/evennia evennia start -l
+#
+#    This will start Evennia running as the core process of the container. Note that you *must* use -l
+#    or one of the foreground modes (like evennia ipstart) since otherwise the container will immediately
+#    die since no foreground process keeps it up. 
+#
 # The evennia/evennia base image is found on DockerHub and can also be used
 # as a base for creating your own custom containerized Evennia game. For more
 # info, see https://github.com/evennia/evennia/wiki/Running%20Evennia%20in%20Docker .
@@ -58,7 +66,7 @@ WORKDIR /usr/src/game
 ENV PS1 "evennia|docker \w $ "
 
 # startup a shell when we start the container
-ENTRYPOINT bash -c "source /usr/src/evennia/bin/unix/evennia-docker-start.sh"
+ENTRYPOINT ["/usr/src/evennia/bin/unix/evennia-docker-start.sh"]
 
 # expose the telnet, webserver and websocket client ports
 EXPOSE 4000 4001 4005