Force node checkBox / radio to the half-checked status. It is valid when [setting.check.enable = true & treeNode.nocheck = false]
1. If you force to the half-checked status, zTree will not automatically calculated the half-checked status about this node.
2. Until you set treeNode.halfCheck to false or null, zTree will automatically calculated the half-checked status about this node.
3. zTree support identification string 'true' & 'false'.
Defaul: false
true means: the checkbox or radio is half-checked when zTree is initialized.
false means: the half-checked status will be automatically calculated
var nodes = [
{ "id":1, "name":"test1", isParent:true, checked:true, halfCheck:true },
{ "id":2, "name":"test2", isParent:true, checked:false, halfCheck:true },
{ "id":3, "name":"test3", isParent:true, checked:true },
{ "id":4, "name":"test4", isParent:true, checked:false }
]