Turn on recursive_triggers by default

[simonw]

https://www.sqlite.org/pragma.html#pragma_recursive_triggers says:

Prior to SQLite version 3.6.18 (2009-09-11), recursive triggers were not supported. The behavior of SQLite was always as if this pragma was set to OFF. Support for recursive triggers was added in version 3.6.18 but was initially turned OFF by default, for compatibility. Recursive triggers may be turned on by default in future versions of SQLite.

So I think the fix for the complex issue in #149 is to turn on recursive_triggers globally by default for sqlite-utils.

Originally posted by @simonw in #149 (comment)

[simonw]

I'm going to make this an argument to the Database() class constructor which defaults to True.

[simonw]

The principle reason to turn these on - at least so far - is that without it weird things happen where FTS tables (in particular *_fts_docsize) grow without limit over time, because calls to INSERT OR REPLACE against the parent table cause additional rows to be inserted into *_fts_docsize even if the row was replaced rather than being inserted.