Add missing options to BuildCmd and set them to match Docker client.

By default the Docker client's build command will set the `--rm` option to `true` so that intermediate containers are cleaned up once the build completes.  This is useful since it avoids cluttering up the list of stopped containers.  I noticed this after I switched gradle-docker to use the API instead of the command line client, so I wanted to bring the two in line.  The API supports this option, so I added it to `BuildImgCmd.java` with a default setting of `true`.

The build API also supports a `-q` option which can be used to suppress output.  By default this is `false`.  This option was added as well.