Construction visual enhancement: Scaffolds during construction

[michael]

Currently, the player clicks the building icon in the unit UI, then places a foundation. Then the unit walks to the foundation, smacks on it for a bit, some dust rises, then the building pops into existence.

The desired enhancement should go like this (the enhancements for this ticket are bolded):

1. Player/unit places foundation.
2. Walks up to it, starts building.
3. Scaffold actor appears (or rises very quickly into place), and dust starts appearing.
4. Building rises up slowly through this as a percentage complete.
5. At 100% complete, the foundation actor disappears, and the scaffold actor either just disappears or drops down quickly (as if dying).

I could see something like this in the building templates:

  <VisualActor>
    <Actor>structures/athenians/barracks.xml</Actor>
    <FoundationActor>structures/fndn_5x5.xml</FoundationActor>
    <ScaffoldActor>structures/construction/scaffold_5x5.xml</ScaffoldActor>
  </VisualActor>

[michael]

Foundation placed (already a feature)

[michael]

Builders begin building. Scaffold quickly rises (or pops) into place. Building will begin rising into place as it is built.

[michael]

Building is nearly completed and is nearly 100% risen.