Inefficient Timer Class

[Christoph Mayer]

The Timer class currently opens up one thread for each timer and therewith creates unnecessary resource overhead. Surely, this can be done more efficiently. There are two options to tackle the problem:

1. Use native timer functionality from the OS
2. Use the SystemQueue with time-sorted ordering and only one interruptable timer that always times the nearest timer. The SystemQueue class has already some internals for this. As timer callbacks need synchronization with the SystemQueue anyways, this would be a nice and clean solution. But certainly tricky to achieve with good performance.