Making the testing Sqoop cascades easier

Got rid of setting MapRedHome in the Cascade
Extracting out the Database specific piece.
Providing a fixed function for data setup and cleanup
I'm sure the documentation is very clear, but I've still seen `Some("1=1")`s in our user's code. I don't think they necessarily understand that `None` is a perfectly valid option. I think it would be best to avoid dummy where conditions, and use `None` and `Some("real condition")` where appropriate. (And make sure we have enough examples to show both styles in their appropriate contexts.)