Expect a string as service result rather than an object

Signed-off-by: Simon Busch <morphis@gravedo.de>
ScreenShooter: when no output path is provided generate one

Signed-off-by: Simon Busch <morphis@gravedo.de>
plugins: add message wrapper class

We're now passing a wrapper around a LSMessage to the callback in order to track the
message object later on. This is for example needed to handle service method
subscriptions.

Signed-off-by: Simon Busch <morphis@gravedo.de>
plugins: add support for subscription handling

Signed-off-by: Simon Busch <morphis@gravedo.de>
Merge pull request #60 from webOS-ports/morphis/work

Morphis/work