flatpak 0.11.5 release.

• Fix a regression which caused installation of epiphany and other apps that export multiple .service files to fail.
• Fix appstream updates in p2p mode.
• Add documentation for the flatpak portal
• flatpak remove is now an alias for flatpak uninstall.
• flatpak uninstall now picks system or user automatically if not specified
• New appstream branch format which is more efficient to distribute, the old is still generated for backwards compat.
• Appstream data now contains compatible arches (for applications that doesn't exist for the primary arch). For example, an i386-only app is now listed in the x86-64 appstream.
• The flatpak version is included in the user agent when downloading.
• The Flatpak-Ref http header is set to the currently installing ref when downloading.
• New argument --timestamp in build-commit-from.
• When updating many apps we now only prune the local repo when all updates are done, making multi-app updates faster.
• flatpak build now always allows multiarch use.
• flatpak build now mounts app extensions during build.
• flatpak build-init now supports --extension to add extension points earlier than build-finish. Also build-finish now supports --remove-extension.
• New flatpak portal allows applications to sandbox themselves and restart a newer version of themselves.
• New flatpak run options: --no-a11y-bus, --no-documents-portal.
• Initial support for end-of-life:ing applications.
• New option X-Flatpak-RunOptions in exported desktop/files allow you to specify no-a11y-bus and no-documents-portal.
• Support for tagged extension points, which is useful if you want to use the same extension id (but maybe different versions) multiple times in an app.
• We now export .service files for names that the app is allowed to own on the session bus.
• libflatpak got new methods for listing remotes by type.
• libflatpak now has support in FlatpakRemoteRef for getting remote metadata such as end-of-life, download size, metadata etc.
• There was some internal restructuring on how installs/updates are done which should improve performance and maintainability.