Improved release notes.

- Format markdown with headers and bullets.
- Split out comments with more than one FIX or FEATURE
- Escape a few characters that disrupt formatting
Merge pull request #2914 from techAPJ/patch-2

user proper naming conversation
FIX: Drupal QA was missing some comments
Delete MIGRATION.md
FIX: Moderators/Admins cannot delete other user's bookmarks
FIX: Do not show unconfirmed users in search results
Merge pull request #2916 from cpradio/pr-unconfirmed-in-search

FIX: Do not show unconfirmed users in search results
Merge pull request #2909 from mcwumbly/release-notes-improvements

Improved release notes readability / formatting
FIX: email replies to closed topic should not be accepted