Add Mode: Dynamically show/hide Event.shortTitle field

[ethanresnick]

Event.shortTitle is a fallback title for the event that's used in cases where there are strict character constraints, such that the event's standard title could be too long. Accordingly, though, when the event's standard title is short enough, there's no need to specify a shortTitle; instead, the title provided can just be used in the character-constrained environments as well.

The API is already smart enough to handle this, which it does by auto-populating shortTitle with the title value if that value is less than shortTitle's maxlength.

But this logic should apply in the intranet too. Namely, when the user's adding an Event, the shortTitle field doesn't need to show up until the title that they enter is longer than Event.shortTitle's maxlength.