Make all kind of timeouts hitting Riak configurable

This branch still has an easy bug, but sending it out to keep tracking. I'd be more than happy if somebody takes this (or it's also fine to omit and start a completely new work).
#743 and #759 were fix for crash caused by timeout. So the assertion here should be `?assertEqual` to check calculation has successfully detected the timeout without crashing. [This timeout setting](https://github.com/basho/riak_cs/blob/develop/riak_test/tests/cs743_regression_test.erl#L36) which is not working any more should be changed to the `storage_calc_timeout`.