Feature: Show blast radius.

This feature does not change the gameplay.
It just entertaining function.
Discussion: http://openxcom.org/forum/index.php/topic,1532.0.html
Added option "battleShowThrowCrosshair" (rendering of the throw trajectory was removed).

![screen039x50](https://f.cloud.github.com/assets/3616568/1109306/f49d8558-197d-11e3-9057-c6235c99a6d5.png)
![screen043x50](https://f.cloud.github.com/assets/3616568/1109309/fa960e26-197d-11e3-9bc0-75f16870f547.png)
![screen040x50](https://f.cloud.github.com/assets/3616568/1109314/04cc2ff6-197e-11e3-80a3-c7331c18e7b4.png)