This commit improves the user experience of different
Document Providers in the app.
In case ext sd card is not present, the option is disabled
in Navigation Menu.
If the device does not support USB OTG,
the option is disabled.
LibreOfficeUIActivity registers a broadcast receiver
in onCreate which detects if a USB device is connected
and directs the user to Settings page to configure it.
In case of errors in configuration in any case,
user is directed to Settings activity after appropriate toast.

Change-Id: I680f78a679e2071ce8330c8168d7aa4e95041723
Reviewed-on: https://gerrit.libreoffice.org/34650Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Aleksandar Stefanović <theonewithideas@gmail.com>