intervals and column order in group_effects and baggr_compare

[wwiecek]

(1) consistently refer to intervals or probs or int
(2) allow for multiple probs to be printed in print.baggr or group_effects
(3) avoid integer indices references to group_effects columns, e.g. see in print_baggr.R:140: study_eff_tab[,c(5, 1, 2, 3),i] as this will break things when we introduce multiple probs.
(4) In baggr_compare when I print the results the order of column and naming conventions are different: homogenise this