* PDO refactor
* Automatic prefix when using the syntax `_tableName`
* Uniformity: MySQL is now PDO::ATTR_EMULATE_PREPARES = false just like SQLite and PostgreSQL, with consequences such as only one statement per query
* Use PDO methods exec(), query(), prepare() + execute() in a more efficient way
* Remove auto-update SQL code for versions older than FreshRSS 1.5 (3 years old)
* The name of the default category is set in PHP instead of in the DB (simplies SQL and allows changing the name according to the FreshRSS language)
* Rename `->bd` to `->pdo` (less of a frenshism, and more informative)
* Fix some requests, which were not compatible with MySQL prepared statements
* Whitespace
* Fix syntax for PostgreSQL sequences
+ MySQL install
* Minor formatting
* Fix lastInsertId for PostgreSQL
* Use PHP 5.6+ const
Take advantage of https://github.com/FreshRSS/FreshRSS/pull/2527https://www.php.net/manual/en/migration56.new-features.php
* A bit of forgotten PHP 5.6 simplification for cURL
* Forgotten $s
* Mini fix custom user config
https://github.com/FreshRSS/FreshRSS/pull/2490/files#r326290346
* More work on install.php but not finished
* install.php working
* More cleaning of PDO in install
* Even more simplification
Take advantage of PDO->exec() to run multiple statements
* Disallow changing the name of the default category
https://github.com/FreshRSS/FreshRSS/pull/2522#discussion_r326967724
Add statistics support for Sqlite by tweeking one query and rewrite an other. The rewrite implied a complete refactor of the MySql query as well.
Now the code is more flexible and make less queries to the database.
See #527
