Merge pull request #830 from nextcloud/fix-fileprovider

Fix fileprovider

src/main/res/xml/exposed_filepaths.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <paths xmlns:android="http://schemas.android.com/apk/res/android">
-    <external-path name="file" path="/" />
+    <external-path name="external_files" path="."/>
+    <root-path name="external_files" path="/storage/" />
     <!-- yes, valid for ALL external storage and not only our app folder, since we can't use @string/data_folder
     as a value for 'path' attribute; in practice, we will only generate URIs in our folders, of course -->
-</paths>
+</paths>