Some Execution fixes

I hit a few issues when using Execution for some example code. One is rather serious.

zip does not work as expected due to the fact that cascading does not allow duplicate head pipes with the same name (it does not assume they are reading the same source, it throws an error).

I am talking to Chris Wensel and hoping to get a workaround, but for now, I disable the zip merging (and just run two simultaneous cascading jobs instead. This works for my tests.