Adds a parameter for the fetch method used by doctrine for the translations

When using doctrine in lazy mode and you need to display a lot record with translations on the same page, every translate call will result in a extra query to fetch the translation that is needed. 

When the fetch mode is set to EAGER, this problem will not occur, but it might have a negative impact on the performance when it is not needed. Therefore the default is still LAZY, and nothing changes in the behavior with this PR.