This commit standardizes the various todos around the code a bit in a manner recognized by LDoc.
Besides drawing more attention by being displayed in the developer docs, they're also extractable with LDoc on the command line:
```sh
ldoc --tags todo,fixme *.lua
```
However, whether that particular usage offers any advantage over other search tools is questionable at best.
* and some random beautification
* [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.
colors were a mixture of 4bpp integers (0=white, 15=black) and
fractional blackness levels (0=white, 1.0=black) before. This is
now unified to use the color specification of the Blitbuffer API.
