New keyword INITIAL TIME for TELEMAC-2D and TELEMAC-3D

In CONDIN and CONDIM, the initial time is set with hard-coded value 0.: AT = 0.D0 If the user wants to change it, the subroutine has to be modified (and compiled). Moreover, if this value is to be changed at several locations of the source codes, it has to be done with care.

This new keyword would be useful if the initial time has to be known before calling CONDIN or CONDIM (e.g. if the atmospheric data file has to be read before with a specific time).