Update release_notes.txt

Version 0.18.0

Fixed msmf preview cleanup and bump to version 0.17.1

version 0.17.0

Version 0.16.0

Merge pull request IntelRealSense#31 from IntelRealSense/v0.15.0

Version 0.15.0

Merge pull request IntelRealSense#14 from IntelRealSense/v0.13.0

V0.13.0

Version 0.12.4 release candidate

Merge pull request IntelRealSense#4 from IntelRealSense/v0.11.0

V0.11.0

Updated release notes