* wip
* wip
* Organize
* Remove unnecessary change in camera_darwin.go filtering
* wip
* Make observer stop safe during startup
* wip IsAvailable impl
* Fix non-darwin builds
* Lock bg loop to main thread and add comment
* Remove fmt prints
* Simplify isAvailable; Add timeout for Read darwin
* Match comment with code
* Change to singleton pattern; Add clearer safer state machine states; Change language from Stop to Destroy; Add new error for when observer is unavailable;
* Add stubs for linux
* Move cancel() up so its not dead code sometimes
* Add stubs for Windows too
* Remove StopObserver usage
* Add camera tests
* Add device observer tests
* Fix multiple destroy calls bug; Call setup in start
* Improve isAvailable
* Improve string handling in device observer c
* Add error handling in example
* Add comment about setup vs start
* Rename and organize device observer darwin
* Explicitly case initial state for setup
* Fix potential destroy goroutine leak; Use only modern build tag; Return err not nil for stubs; Improve comments
* Close startDone channel on device observer stop not wait
David von Wrangel