don't overwrite show templates defined in config

the templates defined in the config under (sonata_doctrine_orm_admin->templates->types->show) were overwritten when the field had a mapping type.
Additionaly I removed the if "collections" by switch statements
Merge pull request #235 from toooni/patch-1

don't overwrite show templates defined in config
Fix double quotes to single quotes in Filter.php
Merge remote-tracking branch 'sonata-project/master'