- fixes platform's COMMENT ON statement support
- implements reverse engineering for column comments
- marks boolean column type commented for distinction

fixes #2182

fixes #2291

Closes #2436

So they get passed to the SQLLogger on `Statement::execute`.

Closes #2261
Closes #2262
Closes #2386

Conflicts:
	lib/Doctrine/DBAL/Platforms/DB2iSeriesPlatform.php

fixes #2270

fixes #1206

Fixed incorrect handling of single quotes in SQL-Strings escaped by repeated single-quote (DBAL-1205)

According to the comment

// deleting duplicated foreign keys present on both on the orphanedForeignKey
// and the removedForeignKeys from changedTables

A check must be had on the $removedForeignKey so it does point on the removed table. Currently it does unset all keys removal even the one pointing on other table.

On the MySQLPlatform::getDropForeignKeySQL table name will not be escaped if the name is passed instead of the object table itself.

Since the getLocalTableName use the localTable property the object is always available, there is no reason not to use it.

The schema's name in the alter session command must not be quoted
https://docs.oracle.com/cd/B28359_01/server.111/b28310/general009.htm

fixes #1352

also refactors URL path evaluation into smaller methods

fixes #1106

When creating sqlite connections from a url with DriverManager, pass the 'path' key the driver expects instead of the 'dbname' key other drivers expect.

fix usage of PDO::PGSQL_ATTR_DISABLE_PREPARES for pdo_pgsql extension setups not built from PHP core

fixes #2249

fixes #1339
closes #921