Add CI tasks that can be run in a Docker container

Enables a Docker based build server to create logsearch dev releases using a command like:

```
docker build -t $JOB_NAME $(pwd)

docker run -e BOSH_TARGET=https://xx.yy.zz.bb:25555 -e BOSH_USER=sudobot -e BOSH_PASSWORD=$SUDOBOT_BOSH_PASSWORD -v $(pwd):/workspace -t $JOB_NAME rake dev_release:create_and_upload_and_deploy
```

Another question - by default won't the build server always be re-creating a dev release as version 1 since it's not saving state anywhere? Would it be better to use `ENV['BUILD_NUMBER']` in the dev release version, when available?