Discuss implementation of sparse modification data

[gvidigal-psr]

• Timeseries in SQLite are indexed by datetime only (confirm?)
• Some models like SDDPSQLite have modification data with an additional block dimension

Questions:

• Should we allow other dimensions like block in SQLite timeseries?
• Should this data be stored in Quiver.Binary instead?
• If stored in Quiver.Binary, should we add a function/flag to read the most recent not-null entry for a given date?