Rebased push of riak_kv#807 (put_merge refactor + EQC)

[russelldb]

Refactor the common put_merge code into riak_object.
Create a EQC statem test for riak_object:merge, reconcile, syntactic_merge that uses Ricardo Goncalves's DVVSet code as a model (https://github.com/ricardobcl/Dotted-Version-Vectors)

This is a rebased push of riak_kv#807. (cc @metadave)

[bookshelfdave]

R16B02b4:[rdb/robj-merge-eqc-rebased]prime:~/basho/riak_ee/deps/riak_kv$ ./rebar eunit skip_deps=true suites=riak_object_dvv_statem
==> riak_kv (eunit)
...
======================== EUnit ========================
riak_object_dvv_statem:57: eqc_test_ (module 'riak_object_dvv_statem')...........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
OK, passed 1000 tests

sibling_count
25.2% 0
15.0% 2
13.9% 1
10.5% 3
9.1% 4
7.0% 5
4.7% 6
4.3% 7
2.9% 8
1.7% 10
1.5% 9
1.1% 12
0.8% 11
0.5% 14
0.5% 13
0.4% 15
0.2% 21
0.2% 18
0.2% 17
0.2% 16
0.1% 20

18.40% {riak_object_dvv_statem,put,4}
18.01% {riak_object_dvv_statem,replicate,4}
17.38% {riak_object_dvv_statem,get,4}
17.36% {riak_object_dvv_statem,get_put,7}
13.01% {riak_object_dvv_statem,update,5}
9.82% {riak_object_dvv_statem,make_ring,2}
6.01% {riak_object_dvv_statem,set_nr,1}
[43.605 s] ok
=======================================================

+1