Fix current resource path /api-docs according with Swagger 2.0 conventions (/swagger.json)

[cabol]

Fix trails routes for:

• Static content (Swagger-UI). What should be the path here? We should avoid any routes conflicts.
• cowboy_swagger_handler. The path here should be /swagger.json directly.

NOTE: The idea is let that path totally configurable, as an environment variable of the app, and default value would be /.

[paulo-ferraz-oliveira]

@elbrujohalcon: does this issue still make sense? I can work on it, if so (I don't fully understand what needs to be done, but...). Otherwise, should we close it (it's been more than 5 years, already).

[elbrujohalcon]

…aaaaand closed!