Add suite server for tracking state for all unit, system, and integration tests

[oubiwann]

Right now, each run of eunit only knows about its own state. What we want is a mechanism for tracking state of all eunit runs, not just the one that's running and will get reported on at the end of its run.

We want a report that will display after all eunit runs have been done, summarizing them.

[yurrriq]

rebar3 to the rescue!