Experimental/class gens ask tell

[jlnav]

Addresses #1240

Approach where the worker itself, outside of calling any user-function, interacts with an ask/gell gen.

1. Initialize the Generator object on the user-side, so they can parameterize however they'd like.
2. Insert into gen_specs.
3. On the worker, evaluate if our gen_f has a .ask. If so, setup the corresponding Runner.
4. Upon "calling" the gen, if the corresponding libE_info indicates the gen is not persistent, simply call the gen's .ask.
5. Otherwise start a familiar persistent loop that asks the gen, sends data outward, and tells responses to the gen.
6. Upon a stop-tag being received, cleanup via .final_tell.

The included functionality test works locally :)