angularjs之ng-option
ng-options一般有以下用法：
对于数组：
label for value in array
select as label for value in array
label group by group for value in array
label disable when disable for value in array
label group by group for value in array track by trackexpr
label disable when disable for value in array track by trackexpr
label for value in array | orderBy:orderexpr track by trackexpr(for including a filter with track by)
【select】指的是 选中value值，
【label】指的是 页面选中项显示内容
【value】指的是 选中项
【group】指的是 分组标签
【array】指的是数组列
对于对象：
label for (key , value) in object
select as label for (key ,value) in object
label group by group for (key,value) in object
label disable when disable for (key, value) in object
select as label group by group for(key, value) in object
select as label disable when disable for (key, value) in object
