Reset xref and dialyzer ignore files

`Particularly if we move to a different version of Erlang, I think it's good practice to start fresh with our xref and dialyzer 'grep -v' files.` 

in favor of https://github.com/basho/riak_cs/pull/658 which I broke the thread by pull-requesting to master :fearful: 

- [x] fix velvet
- [x] fix riak-erlang-client and another
- [x] fix xref (nothing to do)
- [x] discuss on `behaviour_info/1` (and remove the commented out code)
- [ ] review