Suggestion: Migrate configuration to export method

[scottmatthewman]

Currently, the configuration object that governs encoding strategies for dates (and, when #2 is implemented, Booleans) is defined in the CSVTable initialiser.

However, it is only used at the export stage. And it could be argued that it only matters there: the CSVTable is a definition of the structure, and it is only when we solidify that data that we actually care what format to use. This could allow the same CSVTable structure to be encoded in slightly different ways, for example, if Excel and/or Numbers needed slightly different formats than a custom app with its own CSV importer.