Return to Home screen for Kobo devices Mini, Touch and Aura

Added is a case statement in koreader_kobo.sh to cat binary files to
/dev/input/eventx.
Added are three binary files. When the other two files are generated via
mobileread forum users it is easy to expand the script for all models.
Changing directoryname for Kobo files

As requested an all purpose kobo directory.
Kobo Frontlight Tweaks

Now the frontlight remains unchanged from Nickel to koreader and vice
versa.
Also ffi/kobolight.lua has been changed to allow for usage of the toggle
button in the filemanager.
Added Kobo files to Makefile

I can't test on my laptop. Would these changes be enough?
Merge pull request #559 from Markismus/master

Return to Home screen for Kobo devices Mini, Touch and Aura
reorganize launching scripts for both kindle and kobo
so that platform specific files are collected into platform
directory respectively
rename customupdate to kindleupdate in Makefile
Merge pull request #573 from chrox/platform

reorganize launching scripts for both kindle and kobo platforms
add a link to the project wiki in the README file