Need heap size limit for Cerebro

[amhuber]

It would be nice to be able to limit the heap size on the Cerebro process in cases where you want to co-locate it with other components. Should be simple to add using the same logic as 5a555a7.

[amhuber]

Just FYI, the options for Cerebro would look like this:

exec chpst -u vcap:vcap cerebro \
     -J-Xms1226280K \
     -J-Xmx1226280K \
     -Dconfig.file=/var/vcap/jobs/cerebro/config/application.conf \
     -Djava.io.tmpdir=${TMP_DIR} \
     >>$LOG_DIR/$JOB_NAME.stdout.log \
     2>>$LOG_DIR/$JOB_NAME.stderr.log

[Infra-Red]

Added in d88c9df.
Additional options can be passed in the next way:

cerebro.exec.options:
- "-J-Xms1226280K"
- "-J-Xmx1226280K"