controls: Add notification popup
styles: Fix import in base notification style
controls: Set default property to data and don't set default size
controls: Add iconSize property to tool button
controls: Make data the default property for SidePanel

This will allow any kind of children for side panels even non
visual items.
styles: Declare control as var

Will work with any kind of control not only Items.
controls: Declare __control
styles: Cleanup panel style
styles: Fix paths in StyleSettings
controls: Use dedicated style for buttons
controls: Add calendar