Refactor SettingsUI and related modules

submodules/PersistentStringHash/Sources/StringHash.swift

@@ -0,0 +1,12 @@
+import Foundation
+
+public extension String {
+    var persistentHashValue: UInt64 {
+        var result = UInt64 (5381)
+        let buf = [UInt8](self.utf8)
+        for b in buf {
+            result = 127 * (result & 0x00ffffffffffffff) + UInt64(b)
+        }
+        return result
+    }
+}