Added the first couple of functions for the trace daemon.
Design looks as follows:
* we track all processes in an AVL tree
* threads are connected to their main process (as they share a pid)
  * td_thread->next_thread is a linked list with all threads of a process
* each thread has a list of open files

TODO:
* implement syscall handler, plus sample functions
* implement proper process creation
* implement test cases for trace daemon