Use the GApplication API

Uses the GApplication API to handle process uniqueness, message
passing, and lifecycle management. This eliminates the need to
check if xfdesktop is already running and using X to forward events
to the running instance of xfdesktop making it eaiser to port to
GTK3 in the future (as well as GTKApplication).
Workaround g_action_map being too new

This adds in code for g_simple_action_group stuff so that it will
work with glib versions earlier than 2.32.
Wait for the window manager (Bug 7769)

When xfdesktop starts before the window manager the wallpaper images
and icons won't appear on all the screens. This patch waits for the
window manager to start up or 5 seconds before loading the desktops.
Most of the actual checking if the wm is ready is based on a patch
in xfce4-panel, commit-id cabbdfd1c04caf20a71e0af773accf809135a03d
Tell session manage not to restart when quitting
I18n: Update translation da (94%).

201 translated messages, 11 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation da (100%).

212 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
Don't show hidden or backup files on the desktop (Bug 9001)
I18n: Update translation cs (99%).

210 translated messages, 2 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation pt (100%).

212 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation sr (100%).

212 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
Fix icons for .desktop files with absolute paths
Fix icon renames causing duplicate icons

Some programs cause rename move/change/delete events in different
orders. This patch fixes it so there won't be duplicate icons on
the desktop. It also consolidates the icon removal code in the
icon file manager so it isn't duplicated anywhere.
I18n: Update translation tr (98%).

209 translated messages, 3 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation tr (100%).

212 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
xfdesktop-application code cleanup

This patch also works around g_application_quit being too new.
The startup operation can be canceled now, additional comments
added and some sanity checks were added.
I18n: Update translation sv (87%).

185 translated messages, 27 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
Merge branch 'eric/Port-to-GApplication'

Conflicts:
	common/xfdesktop-common.c
	common/xfdesktop-common.h
	src/main.c
Use a label instead of a frame

In the xfdesktop-settings app use just a label instead of a frame
above the icon view in the background tab. This will make it look
consistant with the other tabs.
Add an info bar to the settings app (Bug 10460)

The info bar will be used to notify the user that dragging the
window to another monitor or workspace will allow them to change
those settings. This should help user's customize those settings.
I18n: Add new translation fa_IR (99%).

198 translated messages, 1 untranslated message.

Transifex (https://www.transifex.com/projects/p/xfce/).