Add non-orographic gravity waves drag parameterization (Flott scheme adpated from the Earth GCM)
It can be called using 'calllott_nonoro=.true.' in callphys.def, and set the maximum value of the Eliassen-Plam flux 'epflux_max'.
Cumulated output fields are du_nonoro, dv_nonoro (winds tendency due to GW drag), east_gwstress and west_gwstress (stress profile in esatward and westward direction due to GW drag)
These variables are added in Xhisitns and start files.