Enable explicit assigning of types to columns

[jolmg]

I remember once having trouble with the default type used for columns and having to cast them in the SQL, so it might be nice to have some way to specify types. I'm not sure what the ideal interface for something like this would be.

One simple and dumb idea is to take the CSV header and pass it to sqlite as:

create table $table_name ($header);

that would allow us to optionally specify types and other things in the header. This would fail with quoting in the header, and it would be harder to sanitize the user input.

Another is to somehow include type information in the explicit assignment syntax, but I don't want to over-complicate the code either.