SchemaShell --name and --file params priority fix.

Corrects the two issues identified by #4174 and CakeDC/migrations#183.

I don't currently have the proper test environment set up to run the core test suite locally, so I'm going to let Travis check things for me. I wouldn't be surprised if there is a test to fix somewhere.
I was actually looking for that before! I'm surprised it's not linked in [the Github readme](https://github.com/cakephp/cakephp#cakephp), which is where I looked as I was preparing to (re-)fork the repo with the exact intent of "contributing."

Sure, I can commit to another PR to make CakeSchema uniform, but I suspect there are a **lot** of other files in the project that need that kind of attention still too and honestly I'm not terribly inclined to sign up for that _entire_ job. :wink: Thanks for the feedback.