2010-10-22 : updated docs to reflect all these changes

2010-10-22 : exposed cmor_set/get/has_variable in Fortran interface, just like Python works only on "string" variables
2010-10-22 : add optional "parent_experiment_rip" to cmor_dataset (C,Fortran,Python)
2010-10-22 : fixed bug with variables using "grids" and singleton dimensions
2010-10-22 : upgraded to 2.4 in devel branch
2010-10-22 : exposed cmor_set_variable_attribute to users in Python
2010-10-22 : cell_measures var attribute is now called ext_cell_measures