it is best practice to implement retry logic for transactions that are aborted because of deadlocks or timeouts. this makes such method available inside the DBAL and also add detection for errors where retrying makes sense in the different database drivers

Typo fixes

[DBAL-1220] Fix dropping database with active connection on PostgreSQL

Fixed correct value in "Doctrine\Tests\DBAL\Schema\Visitor\SchemaSqlCollectorTest"

use REGEXP operator for sqlite

Add test for MariaDB 5.5, 10.0 and 10.1 on Travis

Allow testing with doctrine/common 2.6

Fixed typo

Added Postgres 9.4 platform (DBAL-1143)

MySQL getListTableForeignKeysSQL: use current database if null passed

Features and changes:
* jsonb can be used with: options={"jsonb"=true}
* OVER is no longer reserved
* LATERAL is now reserved

DateInterval Type

Travis: Switch to container-based infrastructure

Ref: https://github.com/doctrine/doctrine2/pull/1466

return result from Doctrine\DBAL\Connection::transactional()

Fix call on non-object in ping() with PDO wrapper

Remove git submodules

Fixes an issue when calling `ping()` where `$this->platform` is null. Happened to me because using the `'pdo'` param bypasses the `connect()` method and the platform is never set without explicitly calling the method.

Not sure if this is the most elegant way to deal with this but it worked enough for my purposes so I figured I should submit a PR.

This reverts commit aa4d483f.