added simple DTM and temperature_reading process
temperature reader process periodically reads the temperature from zig001 sensor and sends the temp value to the DTM using events.
Periodically the DTM sends the received temp readings to a server (aggregated in one coap packet)
added temp_interval service to change the interval on which the DTM sends the temp readings
change /temp_interval uri to general /dtm uri, you can specify what parameter you want to change using URI queries.
only temp_interval=X (in seconds) is supported for now.
Merge branch 'coap13' of https://github.com/fvdnabee/contiki-sensinode into coap13