Use bootstrap 4 labels
Use bootstrap 4 labels

Labels are currently used on `<span>` tags, so attaching the label style directly to the button style is simplest.
If this becomes a problem, then the label styles and the button styles should be separated.

TAMULib/LibraryServiceStatusSystemUI,TAMULib/LibraryServiceStatusSystemUI,TAMULib/LibraryServiceStatusSystemUI