Use a linked mysql container instead of running mysql in this container
Remove startup script
Add mysql-data and mysql-db images

Also moves the dw-server Dockerfile and related files from the top-level
to a subfolder `dreamwidth`
Create a one-time setup script

-- /opt/init-db.sh should set up the linked mysql data container, but
doesn't need to be run more than once

-- remove the now unnecessary startup script, and just use mysqld as the
entry point
Pass through the mysql container env variables to the web server

So we can refer to them as $ENV{DB_...} in the config files
Expose the web server logs as a volume
Merge pull request #4 from afuna/mysql-container

Separate mysql into its own container