Time integrator for particle types

[srichers]

It seems that a change from 15 months ago (259db7c) introduced some logic into the initialize_stages function of the time integrators (e.g., https://github.com/AMReX-Codes/amrex/blob/development/Src/Base/AMReX_RKIntegrator.H#L169) that involves a function (CreateLike) that has a different signature for MultiFabs (https://github.com/AMReX-Codes/amrex/blob/development/Src/Base/AMReX_IntegratorBase.H#L137) and ParticleContainers (https://github.com/AMReX-Codes/amrex/blob/development/Src/Base/AMReX_IntegratorBase.H#L25). Because of this, the implementation of initialize_stages only works for multifabs.

To me it seems that either the initialize_stages functions can be specialized to different types or the CreateLike function for particle containers can be given an additional dummy argument to have the same signature as the equivalent functions for multifabs. The latter seems more suitable to me.