add support for overriding the default layout (#2121)

* add support for overriding the default layout
New `overrideLayout` option (if true) will prevent h/w calcs.

* fix error if options are empty

* Implement requested changes
Rename overrideLayout to disableLayout and remove code to unset display

js/reveal.js

@@ -84,6 +84,10 @@
 			// Enable the slide overview mode
 			overview: true,
 
+			// Enable/disable user specified layouts (like css-grid)
+			// (basically prevents all the display & height/width calculations)
+			disableLayout: false,
+
 			// Vertical centering of slides
 			center: true,
 
@@ -1853,6 +1857,8 @@
 
 		if( dom.wrapper && !isPrintingPDF() ) {
 
+			if( !config.disableLayout ) {
+
 				var size = getComputedSlideSize();
 
 				// Layout the contents of the slides
@@ -1927,6 +1933,8 @@
 
 				}
 
+			}
+
 			updateProgress();
 			updateParallax();