This allows us to identify module by their type and it is also better to
store the module type as part of the module instead of having it
hardcoded in factory.hpp
None of the payload fields seem to be used. They were the only place
where EVENT_SIZE was used and why it had to be a macro (no variable
length arrays).
Add a new module that allow users to configure hooks
on received ipc messages. The hook will execute the defined
shell script and the output of the script will be used
as the module content.
Ref #84
