buttonIcons *1.3* ================= Determines which theme icons appear within the header buttons.
Object, *default:* { prev: 'circle-triangle-w', next: 'circle-triangle-e' }
This option only applies to calendars that have the [theme]() option enabled. A hash must be supplied that maps button names (from the [header]()) to icon strings. The icon strings determine the CSS class that will be used on the button. For example, the string `'circle-triangle-w'` will result in the class `'ui-icon-triangle-w'`. If a button does not have an entry, it falls back to using [buttonText](../text_customization/buttonText).