[glob2-devel] towers changes

[Nuage]

I changed the code again (last change for at time). Now it's tuned this way:

0- don't shoot if you can miss the target, wait instead.
1- shoot on the most dangerous warrior, computed by the damage per second.
2- shoot much more likely if the warrior can be killed in one shot. <---he he he
3- shoot much more likely if the warrior is hitting the tower.
4- shoot more likely on a closer warrior.
5- shoot more likely on a damaged warrior.
6- if there is no warrior, shoot on a worker
7- if there is no worker, shoot on a building

Secondly, I did try to address one request stating that towers are not able to
defend anything by themselves. After some tougths I found out that the towers
have properties that are much too differents from units. So I changes the
properties ratio to make them closer of units. Like 5 wheat is needed to builds
the 250 hp of an unit, that is 50 hp per ressource, the first tower get 40 hp
per ressource. As a result one tower level 1 is more like 4 warriors level 1, or
3 warriors level 2.

I made some practical systhetic tests on a special map to balance the value, and
one game to try it. I think it's ok but it's quite a big change and I need your
comments on the overall gameplay changes.

Nuage