Change dataset period from Zero to something more meaningful?

[hansendx]

Copy of #43

These 47 datasets in datasets.csv have a value of 0 for their period. Are all of these "long" datasets?
Which ones can be changed to "1984-2016"?

study	dataset	period	analysis_unit
soep-core	ABROAD	0	P
soep-core	ARTKALEN	0	P
soep-core	BIOAGE17	0	P
soep-core	BIOAGEL	0	P
soep-core	BIOBIRTH	0	P
soep-core	BIOCOUPLM	0	P
soep-core	BIOCOUPLY	0	P
soep-core	BIOEDU	0	P
soep-core	BIOIMMIG	0	P
soep-core	BIOJOB	0	P
soep-core	BIOMARSM	0	P
soep-core	BIOMARSY	0	P
soep-core	BIOPAREN	0	P
soep-core	BIORESID	0	P
soep-core	BIOSIB	0	P
soep-core	BIOSOC	0	P
soep-core	BIOTWIN	0	P
soep-core	CAMCES	0	P
soep-core	CIRDEF	0	H
soep-core	COGDJ	0	P
soep-core	COGNIT	0	P
soep-core	DESIGN	0	H
soep-core	EINKALEN	0	P
soep-core	EXIT	0	P
soep-core	GGKBOU	0	H
soep-core	GRIPSTR	0	P
soep-core	HCONSUM	0	H
soep-core	HEALTH	0	P
soep-core	HHRF	0	H
soep-core	HPFAD	0	H
soep-core	HWEALTH	0	H
soep-core	INTERVIEWER	0	P
soep-core	KIDLONG	0	P
soep-core	LIFESPELL	0	P
soep-core	MIGSPELL	0	P
soep-core	MIHINC	0	H
soep-core	PBIOSPE	0	P
soep-core	PBR_EXIT	0	P
soep-core	PBR_HHCH	0	P
soep-core	PFLEGE	0	P
soep-core	PHRF	0	P
soep-core	PPFAD	0	P
soep-core	PWEALTH	0	P
soep-core	REFUGSPELL	0	P
soep-core	SOZKALEN	0	P
soep-core	TIMEPREF	0	P
soep-core	TRUST	0	P