Don't escape unnecessary strings in exported desktop files. This was breaking gnome-shell app start in some cases.

Fixes issues with /run/user being mounted noexec, which is the default on Ubuntu.

This release fixes a bug where on an update, if nothing had changed the existing installed app deployment would be removed.

Main changes in this release:

• Uses user namespaces in helper, which means no need for setuid. (--disable-userns reverts back to the old model)
• Show origin remote in list-runtimes and list-apps
• /var/cache is writable and ends up in the per-app dir. This helps with fontconfig caches.
• Seccomp filtering of syscall was added
• Some bugfixes

This release breaks the ABI a bit compared to previous version

• /self is now instead /app, which has the advantage of being the same length as /usr (making it easier to relocate things)
• the metadata and command arguments related to permissions have changed
• Added support for metadata specifying persistent directories in the home directory
• Added support for more finegrained filesystem access

This is a minor release with two changes:

• Add profile.d snippet that packagers can use
• Fix an issue with the dbus proxy that broke qt dbus

There are some minor changes here, but the main things are:

• Support for session bus policies
• Support for specifying environment variables in runtime/app metadata