Modification for the working of social-help activity.

This PR introduces the changes required in sugar for the functioning of the social-help activity. The changes are self explanatory and I'm adding a few comments (GitHub ones) in the diiff to explain some of the things. 

This PR is a submission to one of the GSoC 2014 sugarlabs projects.
A dbus-callable method to delegate function calls across different modules. I've used it for a call between sugar-toolkit-gtk3 and sugar.