Implement browserutils plugin(saveViewToFile, generateIconFromFile)

saveViewToFile code was taken(and then modified) from ubuntu webbrowser-app sources:
http://bazaar.launchpad.net/~phablet-team/webbrowser-app/trunk/view/472/src/app/webbrowser/webview-thumbnailer.cpp

Feature #597.
Signed-off-by: Nikolay Nizov <nizovn@gmail.com>