[CINNAMON SETTINGS] Added flickr support for slideshow

Added flickr icon and changed the makefile.am
I think i'd rather keep the flickr button from being sandwiched like it is, maybe (-) packed into a box to the left of that widget, then (+)(flickr) right-aligned,  or (-)(+) left, (flickr) right.

Is the (-) button smart enough to remove the flickr cache?