Designer - Rename actions options to meaningful names

TODO
In Designer

• Rename "operation" to "button"
• Rename "action" to "custom button"
• Replace "button" icon to something more meaningful
• When clicking on + icon in actions, use the premade option
• Show label next to icon (not only for actions but all options)

Update help in actions page

• Custom button:
  Use code to create your custom element and bind it to a button. A typical example is displaying a confirmation dialog that will execute specific logic.

• Button:
  Configure a button and attach an automation chain or script to it.

IMPORTANT - UX IMPACTS AFFECTING OTHER SCREENS

• Show label next to icon whenever + button is used
• Icon for custom option should be used also for other places where we define a custom element: tabs page, left menu item page, main menu pages page.