Add an ExecutionApp trait for objects to skip the Job class

[johnynek]

I've used this in some private code. Seems to work well. Let's you write:

object MyJob extends ExecutionApp {
  def job = TypedPipe.from(List(1, 2, 3)).distinct.writeExecution(TypedTsv("output"))
}

This is the last piece of the modern, functionally pure way to write and run the jobs.

If you want to control have (Config, Mode) is parsed and created, override def config

[ianoc]

LGTM, merge when green