Examples and Tests for Sqoop Execution

1) Included examples for both Sqoop Export and Import with Execution
2) Added tests for the examples
3) Added tests for the SqoopExecution trait especially for the failure scenarios
I basically replicated the behaviour of the existing cascade implementation and don't think we should mix this fix with the Execution implementation. Unless there are any objections, I would like to keep this as it is in this PL.

@mnikliborc from your description I gather multiple SQLs issue will be sort with your PL and you make the maestro changes when your PL is all good?