SUPPORT persistent MySQL DB
DOCKERFILE: do no pre-create DB, do not run db:setup task when building image
DEBUG (MYSQL support)
GITIGNORE: ignore ./logs dir
Persistent external MySQL DB is now supported:

  You can now use external persistent MySQL DB for your GitLab-CI container.
  Launch the instance like so:
   docker run -d \
    -e DEBUG=true \
    -e MYSQL_SETUP=true \
    -e MYSQL_HOST=10.0.0.100 \
    -e MYSQL_USER="gitlabci" \
    -e MYSQL_PWD="gitlabci" \
    -e MYSQL_DB="gitlabci" \
    -e GITLAB_URLS="https://dev.gitlab.org/" \
    -p 9000 anapsix/gitlabci-docker

 WARNING: every time you pass MYSQL_SETUP=true it will overwrite an existing MySQL database
          you should set MYSQL_SETUP=true only first time you start container
          and there is NO DB PRESENT for specified credentials / host / db name
          otherwise, you WILL LOSE

 MYSQL: only MYSQL_HOST variable is required
       MYSQL_USER, MYSQL_PWD and MYSQL_DB will all default to "gitlabci"
       i.e.: docker run -d -e MYSQL_HOST=10.0.0.100 -e GITLAB_URLS="https://dev.gitlab.org/" -p 9000 anapsix/gitlabci-docker

 SQLITE3: to use container-internal ephemeral SQLite3 DB, ommit all MYSQL_* variables
          i.e.: docker run -d -e GITLAB_URLS="https://dev.gitlab.org/" -p 9000 anapsix/gitlabci-docker
Introducting persistent MySQL DB: Merge branch 'develop'