Enhance UO dependency of aux kernels

[YaqiWang]

Reason

When a user object (UO) name is in the parameter list of an aux kernel, the aux kernel will push the UO into a dependency list (with a overloaded function getUserObjectTempl) and later on all the UOs in the list will be put into the PRE_AUX for evaluation. However this resolution mechanism is not ideal because the directly dependent UO may depend on other UOs, which will not be pushed into the list and thus later on will not be put into the PRE_AUX. Users can of cause add a dummy parameter for the aux kernel which accepts all the indirectly dependent UOs. This is however pretty counter-intuitive and users can often forget and consequently see some strange behavior in the calculation.

Design

After talk with @permcody , we believe the solution is in Warehouse, which has the dependency information that can be used when the code put UOs into PRE_AUX. Since the dependency information is not kept currently by Warehouse, I will attempt another simpler solution: overload getUserObjectTempl in UserObject, so that UO itself can know what UOs it depends on. This information can be used in the overloaded function AuxKernel::getUserObjectTempl.

Impact

Make the dependency resolution more complete on the framework side.

[YaqiWang]

The late binding of postprocessors makes things complicated. But I guess it is still doable.