add options to configuration file for testbed component

[mfrey]

we should extend the configuration file for the testbed component. for example

• add support for the various timers
• add support for pheromone configuration (evaporation, reinforcement, initial settings)

[mfrey]

In order to configure the testbed daemon via the command line interface, we have to register functions the following way:

cli_register_command(dessert_cli, dessert_cli_set, "ara_ack_credit_inc", 
   cli_set_ara_ack_credit_inc, PRIVILEGE_PRIVILEGED, MODE_CONFIG, "set value 
     to increase credit on rx ACK");  

and the prototype for the function is

int cli_set_ara_ack_credit_inc(struct cli_def* cli, const char* command, char* argv[], 
   int argc) { ... }