Major Dashboard component update:
* added `admingenerator.dashboard_welcome_path` configuration option (default null), if set, brand text in top navbar will link to that path
* removed unnecesary dashboard files (instead of haveing a default dashboard to extend, you may link to any path useing `admingenerator.dashboard_welcome_path` option)
* added TwigExtension to read admingenerator bundle configuration parameters in twig templates

SingleFileUpload - major translations update