Add BORDER-IMAGE customisation option for all elements

## Prerequisites

- [x] I have searched for similar features requests in both open and closed tickets and cannot find a duplicate.
- [x] The feature is still missing in the latest stable version of Elementor ( Elementor Pro. )

**What problem is your feature request going to solve? Please describe.**
I suggest to add border-image customisation option for all elements (section, column, widgets) like already implemented border and shadow. BORDER-IMAGE property is a great CSS ability to use custom images as borders and it has support by all the browsers.

**Describe the solution you'd like**
In Advanced tab of any item you select image from Media files for border. Then set width, slice, outset numbers and repeat type. Now item have image border.

**Describe alternatives you've considered**

Example
https://jsfiddle.net/vovkasolovev/Lw9e6/

Example of implimentation
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Background_and_Borders/Border-image_generator