Different active visible layers depends on unit type

[Lachu]

I ask for implementing system that switch between sets of visible map layers automatically. It will remember which layers we used for which unit types and restore it, when this kind of unit are activated.

For example:
1. Settlers, workers will see layers with described terrain improvements build for each tile and output of each tile.
2. Military units will see layers describing zoc, military power and native terrain. There's could been also enabled alliance/war layer to see diplomatic status of cities/units.

[Lachu]

Another idea is to create micromanagement layer set, not depending on units, but enabled by some button in UI. In this layer we will see terrain output, only worker/settlers as units, terrain improvements, city production, etc.