move docs into application folders

- required for upcoming Git migration with repository per app / lib
- if nobody complains, I will backport it in a few days to the 4.10 branch also
- I will update trunk/l10n-kde4/scripts/documentation_paths in my next commit

svn path=/trunk/KDE/kdenetwork/kget/; revision=1340343
(cherry picked from commit 3df01812)