[Application] Add Application Management tool

This tool provides a way to list, install and uninstall Applications
using the D-Bus API that will be provided by Crosswalk when it is run
using the run-as-service switch.

Fow now, only listing installed applications is tested. When Crosswalk
implements the install/uninstall functionality, there should be little
to no changes to this tool. But the code is included so the aim of
this tool is made clear.

This tool is implemented using only glib instead of the Chromium D-Bus bindings
to keep this code simpler, the Chromium D-Bus bindings require a separated
thread for handling D-Bus messages.