move some files to more reasonable locations

src/scripts/filesystem.js

@@ -0,0 +1,13 @@
+export function fileExists(path) {
+    if (window.NativeShell && window.NativeShell.FileSystem) {
+        return window.NativeShell.FileSystem.fileExists(path);
+    }
+    return Promise.reject();
+}
+
+export function directoryExists(path) {
+    if (window.NativeShell && window.NativeShell.FileSystem) {
+        return window.NativeShell.FileSystem.directoryExists(path);
+    }
+    return Promise.reject();
+}