Issue 110 : bulkOperations integration tests

Several things to review here :
* the integration tests of course
* some rewrites of the putAll and removeAll methods (with some refactorings too)
Thanks for your input in advance
If find this wording to still be flaky, but I'll leave it for the SPI test to clarify.
Basically atomicity _is_ guaranteed for each function invocation, but not over the entire keySet passed to the bulkMethod