Restructure go project (#2356)

* Move main to cmd
* Move api to internal
* Move logger and manager to internal
* Move shell hiding code to separate package
* Decouple job from desktop and utils
* Decouple session from config
* Move static into internal
* Decouple config from dlna
* Move desktop to internal
* Move dlna to internal
* Decouple remaining packages from config
* Move config into internal
* Move jsonschema and paths to models
* Make ffmpeg functions private
* Move file utility methods into fsutil package
* Move symwalk into fsutil
* Move single-use util functions into client package
* Move slice functions to separate packages
* Add env var to suppress windowsgui arg
* Move hash functions into separate package
* Move identify to internal
* Move autotag to internal
* Touch UI when generating backend

internal/api/context_keys.go

@@ -0,0 +1,16 @@
+package api
+
+// https://stackoverflow.com/questions/40891345/fix-should-not-use-basic-type-string-as-key-in-context-withvalue-golint
+
+type key int
+
+const (
+	// galleryKey key = 0
+	performerKey key = iota + 1
+	sceneKey
+	studioKey
+	movieKey
+	tagKey
+	downloadKey
+	imageKey
+)