[Applications][D-Bus] Use versioning in our D-Bus API

Using the recommendations from here [1] to avoid paiting ourselves
into a corner in regard to our D-Bus interfaces, we add versioning
information to our entry points.

[1] http://0pointer.de/blog/projects/versioning-dbus.html
Merge pull request #1368 from vcgomes/xwalk-interface-versioning

[Applications][D-Bus] Add D-Bus API versioning