Fixed #542: Forward Ctrl key state

When building the CefEventFlags to be forwarded to CEF, consider the
current state of the left and right control key.
Corrected code formatting

Corrected the code formatting issues introduced with
3bb42fe8cbf5248bfa28416e9134930a1e071adb
Also forward Alt and Shift keys

Extended the fix 3bb42fe8cbf5248bfa28416e9134930a1e071adb to also
forward Shift and Alt keys
Merge branch 'master' of https://github.com/ralphmayr/CefSharp into upstream/master
Fix formatting