Ticket #185 :
Created new module containing time variables and subroutines to calculate them. Variables in the time module are public and can be used elswhere in the model. They should not be modified outside the time module.
Note that now each time step have a time interval. xx_start or xx_end values for the date can be used. Previously the date values correspondend to the end of the interval. See description in module time for more information.
These changes do not make any difference in results for couled mode with LMDZ or dim2_driver offline driver.
These modifications also corrects the problem with do_slow related to orchideedriver, ticket #327
