Add JDBC connection string override to sqoop methods

Due to escaping issues with Mortar's generated script I've added the shellwords library to properly escape the JDBC connection string. I added it to lines 316, 358, and 408; admittedly I chose to put it here because I wasn't sure if you'd want it further down the framework; it could easily be put in the Sqoop library at https://github.com/mbrio/mortar/blob/master/lib/mortar/local/sqoop.rb#L107. By moving the `escape` method there the code would be a bit more DRY, but potentially less flexible... maybe?

In any case I'll leave it up to you to decide where the escape method should go.