Implement missing timeline multiselection

Currently with new timeline when multiple rows are selected:

• Delete deletes all selected rows with their child-rows, like previous timeline. Note: If user selects object & its parent-parent-object also unselected parent object in middle gets deleted (which is OK to me, as re-parenting unselected ones could become complicated to implement).
• "Change Time Bar Color" changes color of all selected rows, unlike previous timeline which changes only single bar. Note that if user selects rows with different start color, dialog can default to only one color.
• Dragging rows becomes disabled. Should dragging behave as with earlier timeline i.e. group all multi-selected rows? See Miikka's comment in QT3DS-1454.

Please define how these should behave when multiple rows are selected, which other features would become enabled/disabled, would multi-selection affect timebars moving/resizing etc.