process alternative original MML dir structures

[#53573031]

./src/helpers/md2d/post-batch-processor.rb generates
the following resource which is used to supply the
information necessary to generate the "Original Imported Model"
link in the Interactive browser page.
 
  public/imports/legacy-mw-content/model-list.js

post-batch-processor.rb assumed that the original
content in the sam-activities folder were folders
with folders with one CML file per leaf
inside a folder named: 'original-interactives-in-pages'.

Example:

$ tree -L 1 imports/legacy-mw-content/sam-activities/chemical-reactions/
imports/legacy-mw-content/sam-activities/chemical-reactions/
|-- original
`-- original-interactives-in-pages

However folders that have been committed now have alternate forms:

Example:

$ tree -L 1 imports/legacy-mw-content/sam-activities/DNA-to-proteins/
imports/legacy-mw-content/sam-activities/DNA-to-proteins/
|-- original
|-- page1
|-- page2
|-- page3
|-- page4
|-- page6
|-- page7
|-- page8
`-- page9

The updated post-batch-processor.rb script now handles
this folder structure also and ALWAYS excludes folders
named: 'original'