(20 Oct 2019): DROP BW-compatible, Restruct modules/API, Plan perfect evictions

The first non pre-release for 2.x train.

• BRAKE API: DROP Operation's params - use funtools.partial() instead.

• BRAKE API: DROP Backward-Compatible Data & Operation classes,

• BRAKE: DROP Pickle workarounds - expected to use dill instead.

• break(jetsam): drop "graphtik_` prefix from annotated attribute

• ENH(op): now operation() supported the "builder pattern" with
  :meth:.operation.withset().

• REFACT: renamed internal package functional --> nodes and moved classes around,
  to break cycles easier, (base works as suppposed to), not to import early everything,
  but to fail plot early if pydot dependency missing.

• REFACT: move PLAN and compute() up, from Network --> NetworkOperation.

• ENH(NET): new PLAN BULDING algorithm produces PERFECT EVICTIONS,
  that is, it gradually eliminates from the solution all non-asked outputs.

  • enh: pruning now cleans isolated data.
  • enh: eviction-instructions are inserted due to two different conditions:
    once for unneeded data in the past, and another for unused produced data
    (those not belonging typo the pruned dag).
  • enh: discard immediately irrelevant inputs.

• ENH(net): changed results, now unrelated inputs are not included in solution.

• refact(sideffect): store them as node-attributes in DAG, fix their combination
  with pinning & eviction.

• fix(parallel): eviction was not working due to a typo 65 commits back!