* cmd/syncthing, lib/gui: Separate gui into own package (ref #4085)
* fix tests
* Don't use main as interface name (make old go happy)
* gui->api
* don't leak state via locations and use in-tree config
* let api (un-)subscribe to config
* interface naming and exporting
* lib/ur
* fix tests and lib/foldersummary
* shorter URVersion and ur debug fix
* review
* model.JsonCompletion(FolderCompletion) -> FolderCompletion.Map()
* rename debug facility https -> api
* folder summaries in model
* disassociate unrelated constants
* fix merge fail
* missing id assignement
