Casting in Translation walker

I had problem to coalesce translations wit default values, when the setTranslationFallback was true.
There was a cast for integers so I added cast for Boolean. 
I think there should be a unified way to cast $substituteField to correct type using something 
like 
```
$substituteField = 'CAST(' . $substituteField . ' AS ' . $fieldType->getSqlDeclaration . ($fieldMrthadata, $this->platform) . ')'; 
```