Added a checkbox to enable/diable Keep Aspect ratio.
Options 2 images/slide, 4 images/slide implemented.
UI tweaks: dialog window remembers last used directory (via config),
buttons get enabled/disabled according to the content of the ListBox.
ListBox show filename only, full path is shown lower in a label.
Dialog window reopens again, if slide preview is not in focus.
Added a title slide: author, title.

Conflicts:
	officecfg/registry/data/org/openoffice/Office/UI/DrawImpressCommands.xcu
	sd/uiconfig/simpress/ui/photoalbum.ui

Change-Id: I68d2a3e00f8c55b909fe4d98aa3958188653390e
Reviewed-on: https://gerrit.libreoffice.org/3169Reviewed-by: Andras Timar <atimar@suse.com>
Tested-by: Andras Timar <atimar@suse.com>