Run falco by default in containers.

Instead of running bash as the sysdig container does, run falco. This
makes sense as falco doesn't have a general purpose use like sysdig
does.

To make it easier to run both in docker and as a daemon using the
default command line, enable both syslog and stdout/stderr output by
default. Now that falco dups stdout/stderr to /dev/null when
daemonizing, the stdout/stderr is just thrown away. And when running in
docker, the syslog output will just be discarded unless someone plumbs
the container's syslog output.

Update README.md to reflect that specifying the falco command is not
necessary.

docker/dev/Dockerfile

@@ -46,4 +46,4 @@ COPY ./docker-entrypoint.sh /
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 
-CMD ["bash"]
+CMD ["/usr/bin/falco"]

docker/stable/Dockerfile

@@ -46,4 +46,4 @@ COPY ./docker-entrypoint.sh /
 
 ENTRYPOINT ["/docker-entrypoint.sh"]
 
-CMD ["bash"]
+CMD ["/usr/bin/falco"]