Update Messenger to allow modules to register to multiple message types

[mmoanis]

This pull request attempt to patch the current messenger implementation to allow modules to register to multiple message types at the same time.

The meaning of the messenger class changed from a message broker to a kind of a mailbox where it just keeps the messages until the receiver asks for them.

The stored messages now in the messenger are not only identified by the module unique name but also by the message type_index; this way a module can receive multiple types.

This, however, will break the check if the module has received the required messages or not and required to refactor this check and move it directly to the module itself.

A new method for the module interface isSatisfied will check if the module received the required messages or not.

Note that the message flags are now useless because we can't tell from the messenger or the delegates if the module is satisfied or not.