Force returning some variables in certain cases

[Moohan]

If we're returning more than one years worth of data, we should always return the year variable, even if it wasn't specified in the columns argument.

Other cases would be, when recid or partnership etc. arguments are used, if we are returning more than one, always return the filtering variable. The current code will extract recid etc if it's needed for filtering but then not return it if it wasn't specifically asked for in the columns parameter.