* [device][kindle4] add fake event to kindle4
* modify focusmanager to allow for more complex layout
The focusmanager now naviguate the layout by avoiding nil value
instead of relying on table lenght. It should be completely backward
compatible
* add Dpad naviguation to the touchmenu
* fix crash because virtualkeyboard on non touch device
the kindle4NT has no keyboard nor touch, the fix open the virtual
keyboard so koreader dont crash but it's not useable
* Enable device with keys to use the touchmenu
* Don't get stuck in reader progress statistics plugin
* [underlinecontainer] Fix and remove unused function
References #1898.
* Prevent open screensaver more than one in the same time
* Add option to enable/disable background in message screensaver
* fallback to random images if this book cover is excluded feature + fix Disabled (leave screen/page as it is)
* Autostretch disable by default, more fallback options, leave screen as it is
