Changes

tsk12 Defines a structure and template for the website
Adds the structure of the web project to define the views that will be
part of the public or private part of the application, and where to
locate additional elements such as images or style sheets. It also
incorporates a template composed of a menu, a content and a footer. The
style of the template is created with bootstrap 4, whose dependency has
been added to the pom.
Configures the access and restrictions to the website for each of the
elements of the structure of the web project.
Updates the Contributing file to specify the conventions for the name of
the views and organization of the same.