Make cbepctl parameter options consistent compared with the actual list of parameters that we support in 3.0

There are some mismatches between cbepctl paramter options and the list of configurable engine parameters that we support in 3.0.

We need to make them consistent, so that the couchbase documentation (http://docs.couchbase.com/couchbase-manual-2.5/cb-cli/index.html#cbepctl-tool) should be consistent too.