Added killModule() method and related unit tests

Added a "killModule" method, that removes every ascending and descending bindings between the module and domino.

I also added "test/unit.modules.js", with 7 unit tests checking that communication between domino and a module works well until the module is killed.
Fixed #22: Hacks description

It is now possible to add a "description" strings to hacks. This description is currently just logged when the hack is triggered. It is possible to disable descriptions logging by setting the value of the parameter "logDescriptions" to false.
release v1.2.3