Refactor import config

Remove the path filter, as the content path may not contain a filename.
Disable import when viewing files.
Config can be imported from:
- shared file
- shared text
- vpn:// link

client/android/res/layout/activity_import_config.xml

@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<FrameLayout
-	xmlns:android="http://schemas.android.com/apk/res/android"
-	android:layout_width="match_parent"
-	android:layout_height="match_parent" />