lacy initialization of fileView - in case basic auth is used FileSystem is not yet initialized during the initialize() call

Rather display a dominant div and mark the problematic app in the applist.

Fix #305

Using benchmark_single.php (from administration repo) I can
measure a speed improvement of 5% to 20% loading the /index.php
when logged in. (when using APC and php-fpm).

return 0 instead

The return value almost never changes but this function
is called for every request.

throw exception if encryption was disabled but files are still encrypted to prevent the client from syncing unreadable files