As an audiobook loads, show download progress in TOC chapter menu.

Refer to Step 5 of main flow for patron adjusts settings: https://confluence.nypl.org/display/SIM/Patron+finds%2C+borrows%2C+plays%2C+and+adjusts+settings+for+audio+books+in+SimplyE#Patronfinds,borrows,plays,andadjustssettingsforaudiobooksinSimplyE-4.PatronadjustssettingsonaudiobooksinSimplyE

Acceptance Criteria

• Given user taps 'listen' for an audiobook
• When user views Table of Contents chapter menu
• Then user sees progress of download for each chapter.
  • chapters that have completed download will display as active (selectable), no progress wheel
  • chapters that are downloading show active progress wheel, and chapter is grayed out in the menu
  • chapters waiting to start download show an inactive progress wheel, and chapter is grayed out in menu