jsPanel v4.8.0

• bugfix in option resizeit and panel method resize()
• bugfix in method jsPanel.close()
• added setting "content" to parameter aspectRatio of option resizeit in order to maintain
  the aspect ratio of the content section while resizing a panel
• added support for Font Awesome duotone icons to option iconfont
• added modifier keys to the resizeit feature
• updated z-index handling in modal extension
• updated handling of iframes in the content section while dragging/resizing a panel
• updated event sequence: jspanelcloseduser is now fired before jspanelclosed
• updated option onclosed callback receives a second argument closedByUser set to true if the panel is closed by user action
• updated option onbeforeclose callback receives a third argument closedByUser set to true if the panel is closed by user action
• updated modal extension due to the updated method jsPanel.close()