Checking for adapter's native createParamAccessor

This change makes node-any-db-params check for adapter's native `createParamAccessor()`, as discussed on https://github.com/grncdr/node-any-db-adapter-spec/pull/7#issuecomment-57315898. If there is any, it will be used instead of this modules' implementation.
You're right, sorry for that. Should work better with next commit :).