report_mig_interannual - barchart not generated for some timelaps .... function reformating

The function has been reformated which leads to several breaks in the code, along with that some new developments.

• barchart not generated for timelaps = "2 weeks" or "quinzaine". => fixed
• check that several graphs can be produced by, is this used at all ?

            grid::pushViewport(grid::viewport(layout =
                        grid::grid.layout(length(the_choice), 1, just = "center")))

• fix problem with code in barchart (graphs not right)
• change legend for xlab, currently a factor with the name of the fortnight or name of the day, need to diminish the legend for output
• fix pointrange graph
• fix density graph
• add a choice for year in the plot function
• use things like name = gettext("month", domain = "R-stacomiR") to get the french translation