Most elements should not be selectable and right-clickable

[Tom Chen]

• Nothing should be selectable except <input>s and text in "Help" window
• Nothing should be right-clickable except <input>s and text in "Help" window
• In Multiplayer Mode, user shouldn't be able to click "Connect" button with empty opponent id
• A click where mousedown inside window & mouseup outside window shouldn't close the window (cross-browser hell, I'm not doing this one)
• Tab select a button, press enter to open the window then re-press enter, the window should close
• auxclick outside the window should close the window
• Firefox problem. See also Bugzilla bug 1741231