Helper method `set_IC` for transient multiphysics algorithm

[mkaguer]

Currently, user must manually stack ICs for each of the algorithms and pass through run method. This is tedious and not user friendly. Add a helper method called set_IC() to deal with this.

[jgostick]

If we add a set_IC method to the transient_reactive_transport, then it will be inherited by multiphysics too. This means it should/could be subclassed to take both the values and the algorithm.name to which it applies.