Income boost for Rome changed from 1200 to 1500 per turn to match Carthage

Income for Carthage remains unchanged from all previous versions (1500 per turn)
Income boost for Rome changed from 1000 to 1200 per turn
Income boost for Egypt changed from 500 to 700 per turn
Income boost for Seleucia changed from 600 to 700 per turn

Changed mod icon only

Small boost to Seleucia's income for patch 7 beta. Closer to Egypt but still much less than both Carthage and Rome. Carthage, Rome, and Egypt are doing well in the beta patch but Seleucia struggles. The change is to address this.