Associate Columbus tower's appearance with damage suffered

[sdiaz7]

Define some damage thresholds, and change the tower's appearance once such thresholds have been reached. The point is to make damage suffered more visual.

Implementation details: I am going to define some damage thresholds for the tower at HomeBehavior. Once a theshold is being reached, the script will change the tower's appearance. For doing that, I am going to try to swap its mesh. Since I do not have access to the damaged tower's models yet, I will keep the number of models and the meshes as public variables, accessible through the Inspector. This will let me and others to test the logic without having the models. I expect to have access to the models before integrating.

Definition of Done:

• User can define N damage thresholds, and assign a distinctive mesh to each of those thresholds, through Inspector.
• Once some damage threshold has been reached, Columbus tower's appearance changes to that associated with the reached threshold.
• No change is performed if N=0.

Time estimation: 2 hours.

Branch: dev_Issue172

Pull request: #251

[sdiaz7]

The logic is mostly done, I am currently testing it before opening the pull request.

I've splitted the integration of the damaged tower models into a new issue, #250. This is going to allow me to close this issue even if I do not currently have the models (as commented on the description) and keep the work flowing.

[sdiaz7]

Pull request opened at #251.