Fixed segfault that occured if the environment clock had been changed after RoutingTable constructor
The Environment is now set within its own submodule (prevent mulitple initialization)

Howto handle singleton classes:
http://www.omnetpp.org/pmwiki/index.php?n=Main.CollectingGlobalStatistics
Fixed the OMNeTTimer implementation
Removed the include/omnetpp folder from the standard include folders.

This is neseccary for an effective use of the namespace
If I want to have 2 classes with the same name (and filename) in
separate folders.