Ticket #158
Add option REFTEMP_FILE=NONE and set it to default option: initialize t2m_longterm without reading reftemp.nc. tlong_ref is removed, insted t2m_longterm is ajusted to be in the interval as done for tlong_ref before.
In thermosoil, a second getin for REFTEMP_FILE is done. This variables is now changed into SOIL_REFTEMP_FILE.