Another bug fix, hard on the tail of the last one. This time, though I implemented a few unit tests, so I'm pretty confident there won't be any critical bugs that require another immediate release...

Fixes in this release: boolean type translation was flip-flopped, and there was a problem with NULLs in the database when type_translation was on. The pragma methods in SQLite::Database have been reworked for greater consistency and robustness, and "open" is now an alias for "new", with the second parameter being optional.