XD-2158a Dockerfile and README.md update

* Singlenode README.md updated with instructions on how to create basic streams, open 9393 port and mount directories.
* The Dockerfile updated to create the /tmp/xd/output & /tmp/xd/input directories and change the owner to springxd.  If these directories do not exist when a volume is mounted they will be created by docker but will be owned by "root" and thus can not be written to by springxd.
Markdown edits