WIP support VV context

Conflicts:
	src/riak_dt_map.erl
WIP add vclock context to ORSWOT
WIP context ops to ORSWOT
Add `deferred` operations to orswot for VV only context
Dialyzer fixen
Context disable operations on od_flag
WIP add deferred/context operations to the Map
WIP deferred ops/VV context
Stat test and dialyzer fixes
Add missing fun clause for `add_all`
Add `update/4` to counter and register

Fix bug in Map where removing fields returned at once rather than
running the rest of the ops
Test to ensure deferred ops never remain deferred forever in the case of dead nodes
WIP add context operations to eqc model
Merge branch 'feature/rdb/ctx-ops' of github.com:basho/riak_dt into feature/rdb/ctx-ops
Add context remove of fields to map_eqc test
Update map model to add superceded fields to remove set

Otherwise LWW overwrites with the same timestamp are merged with
predecessors when calculating a value, and the results is incorrect
Address review comments

Add update/4 and parent_clock to behaviour and all mods
Add test for riak_dt_od_flag
Merge pull request #83 from basho/feature/rdb/ctx-ops

Context operations