Start of the refactoring. Commit is quite big because I forgot to use git right from the beginning. Sorry.

 - return the app in privateDataGet
 - implement privateDataDelete
 - split key-value storage from ocs parsing/output so plugins can use it for storage to

fixes http://bugs.kde.org/show_bug.cgi?id=264295

handle the app paramater with private data get correctly according to the spec

still fails under sqlite (and probably postgresql) but I will look more into that later

in the (rare) case that there are unreadable files show an error since it's probably a case of incorrect premissions set by someone.

patch by Debayan Banerjee

Signed-off-by: Matthew Dawson <matthew@mjdsystems.ca>

the callBack class becomes obsolete with these but all places where it is used are updates