add pin option to verbs

[darthtrevino]

In order to enable debugging and complex output scenarios, we can include a pin verb configuration that will flush the verb parquet to disk

e.g.

{
  "verb": "binarize",
  "args": {...},
  "pin": {
     "enabled": true,
     "name": "binarized-data-table",
     "format": "parquet"
  }