Show dead units on the map

After a unit/structure has died, it should have a 'dead' icon on the map for a short period* of time. This would:
1. Let players know who has died where and show if someone actually died on the map
2. Make the map a good indication of the scale of battles
3. *show things like killstreaks, by increasing the delays of death sprites depending on killcounts and cost of unit killed