Made start/stop/crashApp methods (INET 2.2) virtual
Generalized message forwarding, moved TTL check to virtual method
Add method for creation of request message
Included passing of pointer to sending peer when handling messages


* Added UDP address to peer mapping
* New UDPAddress typedef
NED: "destinations" -> "friends"; new friend parameter format

* Renamed "destinations" to "friends", as it fits better
* Separated module name (set in NED/network setup, used only for IP resolving) and node ID (for darknet usage), so there are now 3 parameters: "<module name>:<node ID>:<port>"
Enhanced darknetmessage by custom "toString" method (useful for tracing/debugging output)
Updated .gitignore (exclude compiled files)