* Actually explain *why* we change options, instead of merely copy-pasting
an old version of their description.
* Document the new consecutive_build_service_disable_threshold, which may
be quite confusing at first.
* Do not force options that are not needed with resource classes.
* Remove excessive indentation from the list.
* Small wording fixes here and there.
Change-Id: Ia60fedb8b28936530b24f5f05a654e083fc67499
9935093ead