Modifiers for triggerChars in suggestion menus

[cgross]

We have quite a few suggestion menus and our users are asking that we only show them if they are using ALT or CTRL at the same time since the triggerChars aren't exclusive to the suggestion feature. For ex, the @ symbol triggers a suggestion menu but its also used in emails and other things. We also have the ( symbol as a suggestion menu which could just be for a regular paren. So we'd like to allow the user to say "only trigger the suggestion menu if I'm holding ALT or CTRL.