Unify tags

[ajdapretnar]

Some tags are a bit disjoint. Namely:

• "geo" and "geography"
• "time" and "timeseries"
• "genomics" and "gene expression" (can these two be merged?)
• "medical" and "medicine"

We should also agree on what tags aim to convey. Just the subject field (i.e. biology, economy) and the data type (i.e. text, timeseries, gene expression)? Or additional info, such as task (churn) and specialty (telecom)?