olsr: bump to version 0.6.8

Also:

* Add hash file
* Rename patch to new naming convention
* Revamp/cleanup initscript
* Install sample config to the correct location

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>