Ensure mortar mesh statistics and exodus output possible in parallel and distributed

[lindsayad]

Motivation

It's helpful to know direct information about the mortar mesh regardless of parallel/distributed state

Design

Make sure we can report mortar mesh segment statistics and write exodus output regardless of parallel/distributed state. That means things like parallel communication and robust element and node numbering choices during the mortar mesh generation phase

Impact

More convenience in obtaining "debugging" information when using mortar