🆕 [#56] reinstate User Accounts Switchboard plug (ugly hack)

Due to libgnome-desktop-3 being missing from a repo, we couldn't use packages to get this plug working. However, I pulled these files right from f36 and everything seems to work absolutely fine. This is almost certainly a hacky solution and we should aim to remove it as soon as possible if we do push it into production.

src/common/core-pantheon.yaml

@@ -46,6 +46,9 @@ add-files: [
 
   # /usr/lib64
   ["../../lfs/binaries/debian/indicator-application-patched/0.1/usr/lib/x86_64-linux-gnu/indicator-application/indicator-application-service", "/usr/lib64/indicator-application/indicator-application-service"],
+  ["../../lfs/binaries/misc/switchboard-plug-useraccounts/usr/lib64/libgnome-desktop-3.so.19", "/usr/lib64/libgnome-desktop-3.so.19"],
+  ["../../lfs/binaries/misc/switchboard-plug-useraccounts/usr/lib64/switchboard/system/libuseraccounts.so", "/usr/lib64/switchboard/system/libuseraccounts.so"],
+  ["../../lfs/binaries/misc/switchboard-plug-useraccounts/usr/lib64/switchboard/system/pantheon-useraccounts/guest-session-toggle", "/usr/lib64/switchboard/system/pantheon-useraccounts/guest-session-toggle"],
   ["../sysroot/cores/pantheon/usr/lib64/switchboard/personal/security-privacy-plug-helper", "/usr/lib64/switchboard/personal/security-privacy-plug-helper"],
 
   # /usr/libexec
@@ -68,5 +71,8 @@ add-files: [
   ["../../lib/elementary.icons/apps/32/system-software-install.svg", "/usr/share/icons/elementary/apps/32/system-software-install.svg"],
   ["../../lib/elementary.icons/apps/48/system-software-install.svg", "/usr/share/icons/elementary/apps/48/system-software-install.svg"],
   ["../../lib/elementary.icons/apps/64/system-software-install.svg", "/usr/share/icons/elementary/apps/64/system-software-install.svg"],
-  ["../../lib/elementary.icons/apps/symbolic/system-software-install-symbolic.svg", "/usr/share/icons/elementary/apps/symbolic/system-software-install-symbolic.svg"]
+  ["../../lib/elementary.icons/apps/symbolic/system-software-install-symbolic.svg", "/usr/share/icons/elementary/apps/symbolic/system-software-install-symbolic.svg"],
+
+  # /usr/share/polkit-1
+  ["../../lfs/binaries/misc/switchboard-plug-useraccounts/usr/share/polkit-1/actions/io.elementary.switchboard.useraccounts.policy", "/usr/share/polkit-1/actions/io.elementary.switchboard.useraccounts.policy"]
 ]