[WIP] Add prototype scoping interface to defining a workflow

[cfournie]

This is a prototype interface that would allow one to define the following fork/join graph and (with inherent fork/joins) with the ability to specify actions to perform on error at each "scope" (i.e. wrapped action, sequence of actions, or fork/join of actions).

The following graph doesn't show error handling nodes, but when you don't define error handling for a scope then we exit the current scope and execute the parent scope's error handling (much like exception handling works).

   S
   |
   A
   |
 Fork
 /   \
B     C
|     |
|     D
 \   /
 Join
   |
   E

Not intended to be merged.