A mortalityTable can store additional information to be used e.g. as additional
dimensions in ggplot calls. Typically, these information include sex, base
population, observation year, type of data (raw, smoothed), country, type of
risk, etc. These additional dimensions are stored in the tbl@data list
and will be used by plotMortalityTables and similar functions.
pT.setDimInfo works just like mT.setDimInfo, except that it sets
the information for all sub-tables of the pension table at the same time.