improved (most) icons/image scaling, including avatar scaling

lib/widgets/layouts/empty_page.dart

@@ -27,6 +27,7 @@ class EmptyPage extends StatelessWidget {
                 'assets/info-logo.png',
                 width: width,
                 height: width,
+                filterQuality: FilterQuality.medium,
               ),
             ),
           ),

lib/widgets/mxc_image.dart

@@ -168,6 +168,7 @@ class _MxcImageState extends State<MxcImage> {
               width: widget.width,
               height: widget.height,
               fit: widget.fit,
+              filterQuality: FilterQuality.medium,
               errorBuilder: (context, __, ___) {
                 _isCached = false;
                 _imageData = null;