Merge pull request #823 from chrox/master

disable string collating in Kobo devices
Add "last book" screensaver for Kobo

Epub only.
If someone knows how to get an jpg/png from a pdf on linux (e.g. convert by imangemagick? But i am not a linux specialist and have no idea how to get that one into koreader) I can add something for linux too.
cbz/cbr should be possible too, but I have not looked into it yet.

Do I see it right that the Kindle screensavers are handled by Kindle itself?
But on Kindle you also profit, you can see picture thumbnails now in the search results (long tap on found book)
Show filename on error in crash.log
Allow to take an image from paretn instead of info-i.png
Parameter to turn "last-book-screensaver" off
Add images to info screen
Removed screensaver functions to new lua file
Removed screensaver functions to new lua file
Removed screensaver functions to new lua file
Removed screensaver functions to new lua file
fix OTA update on Kobo, close #824
add image cache
add cover page in sample EPUB file
add getCoverPageImage api for CreDocument
update koreader-base
Merge pull request #828 from chrox/image_cache

add image cache
Merge pull request #829 from chrox/master

markup annotation quadpoints should be defined in counterclockwise
Don't show "0: text" in series view but just "text"
resolve github inconsistencies
resolve github inconsistencies