Blender Git Loki

Fix T48416: Impossible to append from another file without localizing also all indirectly linked data.

Previous to 2.77, this used to be default behavior, was changed in rB591f4549c958b.

However, in most append cases, you do want a full localization of your data, so this new behavior
is kept by default, but there is now an option in append operator to only localize the 'first level'
of data (i.e. datablocks from linked library itself, and not those from other 'sub-libraries').