Plantuml diagram with link support

Description

Plantuml provide a way to integrate link into diagram that can make diagram more interactive.

Proposal

Integrate the links with the two methods :

When the specified format is png, append the map data provided and integrate the usemap attribute to the <img> tag.

When the specified format is svg, use the <svg> data from the svg link instead of putting the url into a <img> tag.

By default use the png and if the map data is not available go to the existing behavior.

Links / references

Description about link in plantuml : http://plantuml.com/link

Example of diagram with links : http://www.plantuml.com/plantuml/uml/XL6zZi8m3Dxp51OxxSw0W6TWEI66q7ERwDouLxjYGBpxEGaI4pqfW-Dy_dwSWwYVTHd9-KvvXXFVu789gjEkRIVoARyr7O-juE-2gSFhzGNTd4CKiBEEXoF5F0LbQWDUQiTbgUs-NZvnP7CskeE0HEmIAm9Xh-ju1-2XOEzHWzKKqu_3z5sQhYgQT7Rmegx85TR7cPaqJj1Rz155_81F41wni9je4PpZ4FJVDDwm0UTgvnsA-sp9VV42dK-moEfUYgvzG2eqaZTCmiqxvy4gc_W3

Map data link of the example : http://www.plantuml.com/plantuml/map/XL6xhi8m3Dtp5HOxT6T0WczWGOZ1jxWamerBxUeEY7yd3mGJHSgGMEVfO6iomax-u7ZqPiEwQGR6Q5FFgrRwHkasKMpfT79Oe8kz3mhfpEDXoo6peB0MW5edBbijD_NnJSDmj4HTWoTcSL6CWAcpURm3G2ZO_s0-tJd4gwDuBaDN7PDrJl2IhiWPrVjUX2qCqANgFQdYXHwWqbDHJwR5S0mNRp_ROC9w6ckSJodfSYHta0bQZ33fx5wAR_g0M6GqRvXLLk-UJm00

Svg link of the example : http://www.plantuml.com/plantuml/svg/XL6xhi8m3Dtp5HOxT6T0WczWGOZ1jxWamerBxUeEY7yd3mGJHSgGMEVfO6iomax-u7ZqPiEwQGR6Q5FFgrRwHkasKMpfT79Oe8kz3mhfpEDXoo6peB0MW5edBbijD_NnJSDmj4HTWoTcSL6CWAcpURm3G2ZO_s0-tJd4gwDuBaDN7PDrJl2IhiWPrVjUX2qCqANgFQdYXHwWqbDHJwR5S0mNRp_ROC9w6ckSJodfSYHta0bQZ33fx5wAR_g0M6GqRvXLLk-UJm00

Documentation blurb

Overview

The benefits can provide a more powerful diagram in order to create for example link to another wiki page that display another diagram and so on..

it's for every user that want to create diagram with plantUML in gitlab.

Use cases

Create a plantuml diagram with links and integrate them in a wiki.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.