Bones : Z-Order To Z-Depth (as discuted in github / commit 4d1c4a40e)

* Change z-order vocable to z-depth for consistency.
* Update code to replace order with depth
* Param descriptor use "bone_depth" internaly

IMPORTANT : This break test project previously created with bones z-order
IMPORTANT#2 : The bone#4 video example should be updated / commented
Fix #741 : Changing quality crash.

CanvasView::quality_spin widget creation has been disable by commit 10c71f0243b.

I have just fixed the crash by commenting a quality_spin reference,
maybe quality_spin should be reactived ?
Rename spal file filter according to other dialogs
Add two dialogs for loading audio and image file form parameter widget
Add image list (*.lst) file support

to Import dialog and Import Image Layer Parameter Panel ->  Filename dialog
Reorder Open and Open history buttons
Code formating.
Rename spal file fileter according to other file chooser dialogs
Select proper dialog according to selected layer.
Add filechooser for render dialog.
Use gtk message dialog
Rename dialog_1,2,3() to dialog_message_1,2,3b()
dialog_entry
Use percision button lable.
Remove unused code
Remove unused code
Use Message dialog instead of general dialog
Use Gtk::MessageDialog instead of Gtk::Dialog for yes_no_cancel three buttons dialog.
Format code style, nothing changed
Have more detailed messages and correct button responses accordingly.

The dialog text (message and button label) are now following the style:
https://developer.gnome.org/hig/stable/writing-style.html.en