Feature/create afc group

@ekate 
This pull request replaces #109 

**Highlights:**
* add examples to test that the `afc_group` is in the list of approved `ArchiveItAccw` `editors`  
* create authorization group `afc_group` 
* configure `afc_group` membership for various environments  
* add scenarios for AFC Group login and metadata edit
* add `AFC_Group` to `features/cassettes/logged_in_users.yml`

**General maintenance:**
* clean up some whitespace in `oai_dc_http_reader.rb`

Finishes #80295342