Gets the registration informations of app_name for the bookmark for uri.
See set_app_info for more informations about the returned data.
The string returned in app_exec must be freed.
In the event the URI cannot be found, false is returned and 
              throws is set to URI_NOT_FOUND. In the event that no 
            application with name app_name has registered a bookmark for uri, false
             is returned and error is set to APP_NOT_REGISTERED.
             In the event that unquoting the command line fails, an error of the ShellError 
            domain is set and false is returned.
| this | |
| uri | a valid URI | 
| name | an application's name | 
| exec | return location for the command line of the application, or null | 
| count | return location for the registration count, or null | 
| stamp | return location for the last registration time, or null | 
| true on success. |