Rework takeScreenShot service method to be functional

Signed-off-by: Simon Busch <morphis@gravedo.de>
Implement service API for set/get the current focused application

Signed-off-by: Simon Busch <morphis@gravedo.de>
Rework for LunaService API changes and add subscription support for getFocusApplication

Signed-off-by: Simon Busch <morphis@gravedo.de>
Merge pull request #52 from webOS-ports/morphis/work

Morphis/work