If the user transfers focus from the topic input box to the Update
button and then uses Enter to activate it, the topic was saved and
a file was opened. This was caused by the Enter key being converted
by the browser into a ClickEvent on the Update button, and it also
being handled by GlobalKey mapping to the FileTable's OpenKeyCommand.
Add a KeyPress handler to the button to trap Enter and prevent it
from being observed by GlobalKey.
Change-Id: Iec2322d7f438ceed2130af0ead10866e01de9391
b502d03cf6