Reader Post: Add receivesCommentNotifications property

[dvdchr]

Depends on: wordpress-mobile/WordPressKit-iOS#452 👈 Please review this first 🙂

Adds receivesCommentNotifications to ReaderPost. This will be used by the upcoming PRs to enable post subscribers to receive push notifications. The default value of the receivesCommentNotifications is set to false because the push notification feature is opt-out by default, so this checks out.

To Test

• Go to the Reader section, and verify that all the posts are loaded correctly.
• Tap one of the posts, verify that the post is displayed correctly.

Regression Notes

1. Potential unintended areas of impact
   Potential crash when parsing the new property?

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Ensure that all the screens depending on ReaderPost objects work fine.

3. What automated tests I added (or what prevented me from doing so)
   n/a.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Generated by 🚫 dangerJS

[peril-wordpress-mobile]

You can trigger an installable build for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[aerych]

Howdy @dvdchr 👋
Looks great! I did a smoke test of the reader and everything seemed to work as expected. Changes to the data model look good to me.
!

[dvdchr]

Thank you @aerych !