Update visibility to restricted via a rake task

[jefferya]

Purpose: create a rake task in the ualbertalib namespace to batch update the visibility property on a set of MediaObjects.

Given an input file with MediaObject ids, one-per-line, update the MediaObject's visibility property

• offers a 'dry-run' capability (by default; to commit changes the -c flag is required)
• addresses #596

Meant to be executed in two stages:

• first stage: dry-run (without the -c flag): to test if the visibility property change will leave the MediaObject in a valid state
  • bundle exec rake avalon:ualbertalib:visibility_restricted -m /tmp/z -c
• second stage: commit (with the -cflag): to commit the change identified by the dry-run
  • bundle exec rake avalon:ualbertalib:visibility_restricted -m /tmp/z