[BUG]: sqlite3 schema type for 'timestamp' is 'TEXT' but should be 'DATETIME'

[puterboy]

Not a big bug and doesn't affect operation of plugin, but the type of the column timestamp in the schema for the energy_data sqlite3 database should be DATETIME and not TEXT

It would be helpful for those (like me) who want to slurp the database into a pivot table to play with it...