Removed old capistrano 2.x config files.

They are no longer needed, transition has been completed to capistrano 3.
Capistrano config: both web and background servers have the "app" role. Custom tasks that previously ran on the "app" role now run in the "web" role.

Now that all servers have the "app" role we can use the linked_files, linked_dirs directives, which work only on servers with "app" role. We still run tasks only in the foreground server by using the "web" role.
Capistrano script now uses the linked_files, linked_dirs directives instead of manually creating folders and linking files and folders from the shared to the current directory.

New folders have been created in the shared folder as necessary. This is a one-time operation.