Tiling2: When adding clients, add them relative to the current one.
Tiling2: When adding clients, add them relative to the current one.

This fixes clients to be added relative to the current one, and not at
the end of the current children list.

This fixes T944.

tasn/enlightenment,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment,rvandegrift/e,rvandegrift/e,tasn/enlightenment,rvandegrift/e,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment