D-Bus support

REVIEW:130003

D-Bus interface to Skanlite. Lets user to get notified on hw buttons press, scan progress and its result. Returns device info, current scan options. Allows changing scan options and storing them as Skanlite config group as separate device-dependant settings profile and switching between them. Allows getting/setting scan area on page.

Includes skanlite.khotkeys file that creates a hotkeys group with predifined hotkeys if imported in KHotkeys app. And two sample scripts demonstration work with Skanlite via DBus interface.