Only order suggestions by count when search is empty

[christophfriedrich]

When you open the component and don't know what to do, ordering by count is helpful to see the most popular options first. But when you type a search query it's more convenient to see the results in an alphabetical order.

(Idea originally came up in #38)

[christophfriedrich]

I guess this is rather easy (setting some prop of the Multiselect component depending on whether there's already input or not should do the trick), so I dared to add the corresponding label.