Database: Behave correctly when inserting booleans

Database: Behave correctly when inserting booleans

Pretty much everything seems to assume that PHP booleans should be
converted to 0/1: MySQL does this implicitly thanks to the lack of
strict mode by default, while PostgreSQL and Sqlite (and Mssql) do it
explicitly.

The addition of MySQL strict mode for unit tests in Ib2873913 exposed
the assumption in the case of MySQL by making some extension unit tests
fail. So let's make casting bool to int the default behavior of
Database::addQuotes().

This also cleans up the phpdoc for Database::addQuotes() to properly
reflect all the supported types that can be passed to it.

Change-Id: I13d0e402fa676bc27c345e8ac12f363ebc627f6a