[addon] Capturing enemy (civilian) buildings

[Krugslayer]

How it should work:
- after capturing enemy military building, you should also capture enemy civilian buildings with workers inside and goods inside
- buildings placed on a borderlines should be destroyed (no change here)

How to enable this addon:
- this addon should be optional. Should be available like other RttR addons (in options).

Why this addon:
Capturing enemy civilian buildings is a logical choice. Why burn everything and waste your own materials (and time) to build your own buildings when you can use the existing ones. You can save your own building materials, time and also steal the goods that your opponent has. This addon could be especially very useful on big maps, when you have big empire and you simply don't want to run out of your own resources (especially stones*) so fast. Realistic and historically logical option, which (IMO) will make this game more interesting.

*this addon should work well with paved roads addon

[Spike (fvv1)]

https://github.com/Return-To-The-Roots/s25client/issues/121