addCondition now can be used with "OR" conditions too

Example:
```
$m->addCondition(array(
array($q->expr('now()'),array(1,5,7)),
array('doc_prepared',$m->getField('doc_sent')),
$q->expr('foo()'),
))->addCondition('name','like','%SIA%');
```

will generate following SQL:
`WHERE (now() in (1,5,7) OR doc_prepared=doc_sent OR foo()) AND name
like
'%SIA%'`

Model fields doc_prepared and doc_sent can be calculated fields too :)
Merge pull request #528 from DarkSide666/master

addCondition now can be used with "OR" conditions too