Switch to side-by-side view

--- a/src/qtgui/recoll.pro.in
+++ b/src/qtgui/recoll.pro.in
@@ -14,7 +14,7 @@
 
 FORMS	=  recollmain.ui \
 	advsearch.ui \
-	preview/preview.ui \
+	preview.ui \
 	sort.ui \
 	uiprefs.ui \
 	ssearchb.ui