Added MarkClean method to reset RiakObject's internal hash code for comparision & marking as dirty.
Added MarkClean method to reset RiakObject's internal hash code for comparision & marking as dirty.


Former-commit-id: 75c1529d5becdbed949a4ce5c7a5cf0123fbf215
basho/riak-dotnet-client,basho/riak-dotnet-client,rob-somerville/riak-dotnet-client,rob-somerville/riak-dotnet-client