[Fixes bug #1175733] Layer preview updates immediately after an image is pasted
Refresh layer preview after paste image action without adding extra history items
Modify FinishSelection to avoid code duplication (in RedrawLayerPreview)
Remove call to Invalidate since it's already part of FinishSelection
Merge pull request #56 from ericksson/master

[Fix for bug #1175733] Update layer preview after pasting.