Minor UI tweaks and clean up project.

imports/Spectral/Dialog/OpenFileDialog.qml

@@ -0,0 +1,13 @@
+import QtQuick 2.12
+import QtQuick.Dialogs 1.2
+
+FileDialog {
+    signal chosen(string path)
+
+    id: root
+
+    title: "Please choose a file"
+    selectMultiple: false
+
+    onAccepted: chosen(selectFolder ? folder : fileUrl)
+}