Querybuilder for communibase?

Initial build for a doctrine-like querybuilder for use with communibase....This would allow far more complicated queries to be built without loosing too much readability

i.e.
```
$qb = new \Communibase\QueryBuilder();
$qb = $qb->add($qb->expr()->eq('groupId', 'adf'))
		->add($qb->expr()->lt('startDate', date('c')))
		->add($qb->expr()->orX([
				$qb->expr()->gt('endDate',  date('c')),
				$qb->expr()->eq('endDate', null)
]));
```
instead of
```
$memberships = $this->connection->search('Membership', [
			'groupId' => ['$eq' => 'adf'],
			'startDate' => ['$lt' => date('c')],
			'$or' => [
					['endDate' => ['$gt' => date('c')]],
					['endDate' => null]
			],
		]);
```

The first being able to inject extra stuff more easily ?

Its derived from the Doctrine ODM Querybuilder...