Import survey metadata

[rbroth]

Most of the surveys are missing metadta. So far, we are importing:

• Fourth Integrated Household Survey (IHS4)
• Ethiopian National Micronutrient Survey
• malawian women biomarker survey

For each of these (and any future dataset) we want to record:

• Name
• publication date
• date when the survey started
• date when the survey ended
• the geographical area covered by the survey
• Other information we want to provide to end users, e.g Whether biomarker measurements were taken from blood plasma or blood serum