[Centurions] Centurions can be drag'n'dropped between the pile and the boarding track.
[Refactoring] this.id added in view classes, instead of getting it from the model each time.
[Space] Top left space zone ships added (except piloted vipers).
[Ships] Ships can be dragg'n'dropped between pile and top-left zone.
[Space] Basestar can be drag'n'dropped, and damage tokens added.
[CSS] CSS splitted in two files, one for images, one for global styling and positioning.
[Space] Damages can be drag'n'dropped on basestars.
Merge branch 'develop' of github-elistas:aurelien-defossez/pegasus-master into develop