CSS - add .extra-wide classes to set max-width much higher when it's active

.extra-wide .entry-header,
.extra-wide .entry-content,
.extra-wide .entry-summary,
.extra-wide .entry-meta
functions.php - add gv-extra-wide to metadata manager settings
functions.php - add gv_filter_post_classes_extra_wide() to insert .extra-wide in post classes when the postmeta box is ticked and add gv_filter_sidebars_widgets_extra_wide() to remove widgets from sidebar-2 when extra wide