Update PureBoot images to heads-beta-8

Signed-off-by: Matt DeVillier <matt.devillier@puri.sm>

changelog.md

@@ -2,6 +2,27 @@
 
 This document provides a brief chronological summary of Purism Librem firmware releases, and the changes in each build/release.
 
+### PureBoot heads-beta-8
+2019-07-19
+
+* Fixed spurious error re: mounting efivarsfs
+* Removed duplicate MOTD at startup
+* Changed MOTD from HEADS to PUREBOOT
+* Streamlined ROM hash generation for non-TPM devices
+* Revised main menu items for clarity
+* Added newlines for improved readability in console output
+* Added prompt to update /boot checksums after adding a new GPG key
+* Fixed error/warning background colors on Librem 15v3/4 devices
+* Fixed boot device/user config not persisting when GPG key added
+* Improved handling of missing/invalid boot device on startup
+* Added GPG menu option to replace existing key(s)
+* Added a Full Reset option to remove all GPG keys, boot signature/checksums, and user config
+* Improved error handling when persisting GPG/user config items
+* Changed default to Y when selecting to change the default boot selection
+* Added a retry prompt when Librem Key detection fails
+* Fixed not handling user cancellation when adding a GPG key
+* Improved detection/handling of non-TPM boot flow
+
 ### PureBoot heads-beta-7
 2019-05-27