Improve usability and style in web export presentation

- Check for WebGL support, don't load if unsupported
 - Check for IndexedDB support
 - Make canvas support check message visible
 - Colored debug output for warnings and errors
 - Make it obvious status can be closed by clicking
 - Don't use status to display non-critical errors
 - Limit output message count
 - Add clear output button
 - Fix setting total memory

platform/javascript/export/export.cpp

@@ -377,7 +377,7 @@ EditorExportPlatformJavaScript::EditorExportPlatformJavaScript() {
 	logo->create_from_image(img);
 	max_memory=3;
 	html_title="";
-	html_font_family="arial,sans-serif";
+	html_font_family="'Droid Sans',arial,sans-serif";
 	html_controls_enabled=true;
 	pack_mode=PACK_SINGLE_FILE;
 }