网格am-g,am-u-sm-*,am-u-md-*,am-u-lg-*;最大宽度1000px am-g-fixed;不足 12 份的网格,需要在最后一列上添加 .am-u-end;小于中屏显示am-show-md-down;仅大屏显示am-show-lg-only;小于中屏隐藏am-hide-md-down;列边距,距离前列的距离am-u-sm-offset-*;列居中am-u-sm-centered;大屏时列居中am-u-lg-centered;小屏中屏列居中,大屏不居中am-u-sm-centered am-u-lg-uncentered;列排序am-u-md-push-* am-u-md-pull-* am-u-lg-reset-order;