Hide hs.chooser result list when it's empty

[zzamboni]

I think it would be nice to have an option for the chooser to start with just the entry field showing, and expand to show the matches once the user starts typing - similar to the way Spotlight, Lacona or other choosers work.

[zzamboni]

Just noticed that this is mentioned in #1149 as well.

[ashfinal]

Just tried hs.chooser:rows(0). It had extra space, which I think not elegant.

[zzamboni]

@ashfinal Also, you cannot change rows() on the fly (while the chooser is displayed), which is the first thing I tried.

[cmsj]

I would love to have the results panel appear/disappear automatically depending on whether there is anything in the table, and I've tried at least 3 times to make it happen, but my AppKit-fu is not strong enough to make it work.

Anyone who understands AutoLayout stuff, or has other tricks for these things, is very very welcome to help!