amr2cube is already used somewhere in RAMSES

remove unused pieces of code

output on a unit instead of OUTPUT_UNIT or ERROR_UNIT

Now read the data
Should be tested

Introduce 2 classes
one class for hydro header
one class for hydro data
modification in the hydro reading files

first version of read_ramses_hydro_header written

Commit to save changes before updating my system

name of functions and modules changed

First commit for some files, everything is still to be done