* Add blender_downloader.py
* Add engine_manager.py
* Add additional methods to engine_manager.py
* Refactor file layout to make engines on par with workers
* Add system platform info to status response
* Default to using system platform / cpu if none are provided
* Add API to download an engine and some general cleanup
* Add method to delete downloaded engine
* Add API calls to download engines and delete downloads
* Misc fixes
* Add background fetching to server_proxy
* Update UI to use server_proxy fetched jobs
* Fix issue getting status with empty jobs_cache
* Fix issue with jobs not appearing after switching servers
* Remove job_cache from dashboard_window and utilize server_proxy caches
* Remove jobs from table that shouldn't be there
* Streamline how we're handling offline tracking and handle connection error when fetching thumbnail
* Add ability to remove any manually added servers