Next computation with a wind, water depth or current given by a file

This merge request is the solution found for the issue #907 (closed). When using a variable (wind/ water depth/ current) read in a file (generally coming from telemac2d), if a hot start was done the variable was not interpolated in time anymore between two time read in the file for the time step of the calculation. This was coming from a bad initialization of the reading, at the hot start. lecsui.f has been modified so that the initialization is good.

Some new test cases in the case Next_Comput have been created to test the functionality and to show that the interpolation is done for tide or wind. The figures have been integrated in the documentation case.