User related messages

• improve and generalize biomod2 test functions (prefixed .fun_test[...])
• standardize / uniformize all cat, message, stop and warning messages

Other improvements

• update default parameters in functions (set to NULL if possible)
• add seed.val parameter in bm_CrossValidation
• add check in BIOMOD_Projection and BIOMOD_EnsembleForecasting to deal with single model projection failing
• fix kfold selection for non-binary data in bm_CrossValidation
• add check in bm_PseudoAbsences to select presences in PA.user.table when user.defined strategy
• fix bm_Tuning for DNN : multiple sets (PA x RUN), hidden width and depth parameters
• fix EMwmean for abundance models using RMSE, MSE, MAE or Max_error as selection metrics

Full changelog can found here