Never return more than 4 image objects per sub-album
Never return more than 4 image objects per sub-album

Fixes #79
(cherry picked from commit b2b29a5)

owncloud/galleryplus,IATkachenko/gallery,owncloud/galleryplus,patman15/galleryplus,IATkachenko/gallery,desaintmartin/gallery,interfasys/galleryplus,owncloud/galleryplus,owncloud/gallery,desaintmartin/gallery,setnes/galleryplus,imjalpreet/gallery,leftees/galleryplus,tahaalibra/gallery,patman15/galleryplus,efueger/galleryplus,tahaalibra/gallery,setnes/gallery,viraj96/gallery,setnes/galleryplus,setnes/gallery,imjalpreet/gallery,setnes/gallery,setnes/galleryplus,viraj96/gallery,patman15/galleryplus,leftees/galleryplus,desaintmartin/gallery,interfasys/galleryplus,owncloud/gallery,viraj96/gallery,IATkachenko/gallery,tahaalibra/gallery,efueger/galleryplus,imjalpreet/gallery,interfasys/galleryplus,owncloud/gallery,leftees/galleryplus