Release 1.7.1

This is the first release in the 1.7.x unstable release series.

A major change is that the support for the ostree peer-to-peer installation has been
simplified. Flatpak no longer supports installing from local network peers, and sideloading
from local usb stick is no longer automatic. To enable sideloading you have to configure
a sideload repository by creating a symlink to it from /var/lib/flatpak/sideload-repos or
/run/flatpak/sideload-repos. Due to this the flatpak code has been simplified internally
and the p2p support is more efficient.

Other major changes

• If an app has filesystem access, the host /lib is accessible as /run/host/lib, etc.
• New filesystem permission "host-etc" and "host-os" give access to system /usr and /etc.
• Flatpak now uses variant-schema-compiler to generate more efficient code for
  parsing GVariant files from ostreee.
• libsystemd use is now optional in configure.
• Journal sockets are mounted readonly
• document-export now supports exporting directories (requires new portal version)
• DConf migration now allows version numbers in object paths

$ sha256sum flatpak-1.7.1.tar.xz 
aae66b0770154b31ea48e5b53060e9ca2a1b656cd322546a43730c77ea63885b  flatpak-1.7.1.tar.xz