[AppStream] AppStream-glib 0.7.7

[Richard Hughes]

Version 0.7.7
~~~~~~~~~~~~~~
Released: 2018-03-12

New Features:
 - Add AS_IMAGE_LOAD_FLAG_ALWAYS_RESIZE to always resize the pixbuf
(Richard Hughes)
 - Add custom metadata key for shell extension uuid (Kalev Lember)

Bugfixes:
 - Always resize AppStream icons to fit the destination size (Richard Hughes)
 - Correctly validate files using OR in the metadata_license (Richard Hughes)
 - Do not fail to validate if the timestamps are out of order (Richard Hughes)
 - Don't abort the build if pngquant fails (Richard Hughes)
 - Update the SPDX license list to v3.0 (Richard Hughes)

Richard