Refactor for better modularity (share more code among edit functions, rename "offline" package to "backend"

src/backend/2globalsUNIX.go

@@ -0,0 +1,14 @@
+//go:build !windows
+
+package backend
+
+// EntryRoot path to libmutton entry directory
+var EntryRoot = home + "/.local/share/libmutton"
+var ConfigDir = home + "/.config/libmutton"
+var ConfigPath = ConfigDir + "/libmutton.ini"
+
+// PathSeparator defines the character used to separate directories in a path (platform-specific)
+const (
+	PathSeparator = "/"
+	Windows       = false // TODO temporary, remove after native sync is implemented
+)