Low precisions when writing the grid files (in gridio.c)

[guiaug]

When splitting the grid for each process, the functions in gridio.c write non-integer values as "%e", which is single precision.
If the UTM grid is not centred, the coordinates written in the files, and read by the processes when starting the run, are low resolution. The coordinates can be 1 meter precision depending on the location of the domain.
Replacing "%e" by "%lf" in gridio.c would do the trick.