WIP: Threadcommunicator

Currently segfaulting in a few tests randomly on prism:

• function_test
• expression_integrator
• heat_eqn_integrator

There is no problem on my laptop.

This will require downstream testing for compatibility & correctness with:

• ODT - currently segfaulting particle tests
• Wasatch
• PoKiTT

See also James_Research_Group/SpatialOps!1, which must be merged simultaneously.

Note that when running multithreaded:

• ctest should not be run in parallel since that can dramatically slow down the execution times.