New Causal-LWW Register

Based on dvvset.erl from https://github.com/ricardobcl/Dotted-Version-Vectors

Looking for feedback, and maybe help from someone to make the crdt_statem_eqc test for this, which I'm slightly lost by.

Also, waiting to hear back on whether or not I can even include dvvset.erl (due to licencing issues)