feat(cmd/tblconv): support table initialization for new db instances

[Zaba505]

Currently, the target table for writing data to must be initialized before tblconv can be used to write any records into it. For example, the following command will fail if the foo table isn't already present in the sqlite database.

tblconv csv into sql -s sqlite -q "insert into foo(id, name) values (?, ?);" data.csv