Internal functions to parse mode.slot strings
get.mode.slot(data, mode.slot, allow.ntr = TRUE)
a named list with elements mode and slot (or only slot in case of ntr,alpha or beta)
a grandR object
a mode.slot
whether to allow for the value "ntr" (and throw an error in case)
A mode.slot is a mode followed by a dot followed by a slot name, or just a slot name. A mode is either total, new or old