Start phosh via gnome-session

Start a full gnome-session as gnome-shell does.

To get out of WIP status:

• Check on dev board or qemu

data/meson.build

+desktopconf = configuration_data()
+desktopconf.set('bindir', bindir)
+desktopconf.set('libexecdir', libexecdir)
+
+desktop_files = [
+  'sm.puri.Phosh.desktop',
+]
+foreach desktop_file : desktop_files
+  i18n.merge_file('desktop',
+    input: configure_file(
+      input: desktop_file + '.in.in',
+      output: desktop_file + '.in',
+      configuration: desktopconf
+    ),
+    output: desktop_file,
+    po_dir: '../po',
+    install: true,
+    install_dir: desktopdir,
+    type: 'desktop'
+  )
+endforeach
+
 runconf = configuration_data()
 runconf.set('bindir', bindir)
 runconf.set('libexecdir', libexecdir)