modified evaluation data structure to use a Queue, now output triggers do not call code directly but call a function that pushes another delegate Task object to the Q, then using information in the task object the stack will yield in the correct way and continue executing.  Will need to verify that code stays in sync between stack and code that is adding delegates/closures to Q.

also adding start execution node that requires no dependency.

still need to solve output intermediate variable issue, so that when each trigger is executed from the Q, the output variables are regathered from the python or other eval context.