[Enhancement] Add constructFunc=init support to make construct function more clear.

[LaurenceLiZhixin]

Now our construction function's mark is like:

// +ioc:autowire=true
// +ioc:autowire:type=normal
// +ioc:autowire:paramType=Param
// +ioc:autowire:constructFunc=Init

Param.Init() is registered as construct function. But sometime there is no need for param, developers can use a simple function to create object like.

func constructFunction(impl *MyObject)(*MyObject,error){
    impl.ID = "xxx"
    return impl, nil
}

We should support both marks:

// +ioc:autowire:paramType=Param
// +ioc:autowire:constructFunc=Init
// to use Param.Init() as construct function with loaded params.

// +ioc:autowire:constructFunc=myConstructFunction
// to use myConstructFunction() as construct function.