Merge Draco-7_15_0 to develop

[clevelam]

Background

• Merging the draco-7_15_0 release branch back to master

Description of changes

• Update change logs and release numbers
• See Milestone 5 for release details

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • [ ] Travis/Appveyor CI checks pass
  • [ ] Code coverage does not decrease
  • [ ] Valgrind test passes
  • [ ] Toss3 checks pass
  • [ ] Trinitite checks pass
  • [ ] Code reviewed/approved, sufficient DbC checks, testing, documentation