CAMITK_WARNING: pop up message window, add Esc shortcut

About you:
Arthur Derathé

Product: Surgery Evaluation Environment

Overview:
It's more for convenience as a user in camitk-imp before, with QMessageBox::warning, the window displaying the message could be closed with the "Enter" and the "Esc" buttons. Now with the camitk logger, it's only possible to close it with "Enter".

As my interface requires already a lot of clicks, it would be much appreciated to regain this feature!