testing section 1.1 Typical Usage Of Core Routines And Objects
 - execute() no longer has failure conditions, so remove SqliteError() layer
 - column_text() needs &mut self
   - consequently, so does FromSql::from_sql
 - oops! neglected to unwrap column_text() results in FromSql for String
 - core module doc now has convenience and typical use tests
   - also maintained as tests/typical.rs integration test
     where dev tools grok better
 - existing-or-new test TODO
 - reorganize main lib doctest a bit
   - also maintained as tests/ex.rs
     - clean up some debug println!()s