merge PR #959
add new flags (burkina faso + madagascar)
Update admin_ui.es.yml #960
exporting empty belong_to field does not break the whole csv
add ukrainian locale
Merge remote-tracking branch 'timsly/uk-locale' into v2.5.x
Revert "Merge remote-tracking branch 'timsly/uk-locale' into v2.5.x"

This reverts commit f886e983ce6b9a11917947c8c845b5e8f7773b25, reversing
changes made to a104ef28a7fe44300395afa59163e449ead61968.
Portuguese translation (pt)
pt flag
fix pt yml
export now big chunk of content entries + pagination of content entries even works with a large number of entries
fix bug: Can not query content_entries via the Restful API #964
forgot to apply the collection_empty? method to content entries
add indexes to the content entries collection
add better mongodb indexes for the content_entries collection + use an optimized version of the max aggregation method
improve performance when getting the next unique slug of a content entry
translations were not scoped by a site
next version will be 2.5.6
New liquid tag: model_form #983
Remove case sensitivity when linking memberships/accounts