Avoid two booleans in a row for CreateDatabase signature

[sl-at-ibm]

As discussed in PR #115 :

[avoid] having updateDbKeyspace and waitForCompletion be top-level boolean params since they can be a bit confusing when not used with named method params.
It's probably out of scope for this PR, but just having something like BlockingCommandOptions which extends CommandOptions and the aforementioned options could be clearer to use.

[sl-at-ibm]

@toptobes I am doing this one right now.