Refinements to chevrons in facet design

[astridu]

Could we use this bootstrap icon for the chevron? it's slightly more contemporary looking

Also, the chevron should be pointing down when it's collapsed to indicate the information will flow down when the chevron is clicked, and it should point up when the section is expanded to indicate the information will move up and be hidden. Thank you!

[jcoyne]

I believe this is done in Blacklight 9.