Cleanup physiq

[emillour]

physiq_mod.F has become really large and difficult to read.
Among possible foreseen improvements:

• replacing repeated use of pu,pv,pt,.. with tendencies pdu,pdv,pdt, etc. with (local) updated values zu,zv,zt,... see ticket #60
• cleanup in the outputs with writediagfi: get rid of many of the if/else around calls to writediagfi (since diagfi.def is used to select outputs) and of the redundant 3D/1D output sections (writediagfi should manage being in one or the other situation)