feature request: write_record / read_record to read/write a single row from a record instance

[kleinschmidt]

In many different contexts we are using Legolas to read/write single-row tables as a way of de/serializing record structs. As a result, I fidn I'm frequently copy-pasting the same boilerplate code (wrap the row in a vector, get the schema version, Legolas.write, Legolas.read, only(Tables.rows(tbl)), get the record type, construct teh record).

Having a (read|write)_record (or maybe (read|write)_row?) methods defined here woudl reduce this duplication a lot.

see also: beacon-biosignals/LegolasFlux.jl#24