[Bf-committers] Collecting fixes for "2.66a" release.

[Campbell Barton]

> 54903 - what does it fix from user perspective?

Thought my commit log explained this well enough.

If you instance group objects from a scene they now use their original
layers, rather then setting all layers - requested by the guys making
`Naughty 5` (very safe change)

Also select newly drag'n'dropped objects rather then just making
active. (active+unselected is OK but a bit confusing to create this
context by default).