#119, #72: All elements and relationships can support hyperlinks (based on #126)

[kirchsth]

Hi,

I created a new PR based on #126 with link support. It should cover #119 and #72.
I didn't merge the links support into #126 that the link extensions can be rejected.

I extended all calls with a $links="..." that all elements and relationships can have a link like below

@startuml
!include https://raw.githubusercontent.com/kirchsth/C4-PlantUML/extended/C4_Container.puml

Person(admin, "Administrator", $sprite="person2", $link="https://github.com/plantuml-stdlib/C4-PlantUML/blob/master/LayoutOptions.md#hide_person_sprite-or-show_person_spritesprite")
System_Boundary(c1, "Sample System", $link="https://github.com/plantuml-stdlib/C4-PlantUML") {
    Container(web_app, "Web Application", "C#, ASP.NET Core 2.1 MVC", $descr="Allows users to compare multiple Twitter timelines", $link="https://github.com/plantuml-stdlib/C4-PlantUML/blob/master/LayoutOptions.md")
}
System(twitter, "Twitter", $link="https://github.com/plantuml-stdlib/C4-PlantUML")

Rel(admin, web_app, "Uses", "HTTPS", $link="https://plantuml.com/link")
Rel(web_app, twitter, "Gets tweets from", "HTTPS", $link="https://plantuml.com/link")
@enduml

png itself supports no links, therefore the following image is generated as svg image.
Github does not support svg links in Markdown.
If you click on the image a new window is opened and there you can use the links.

The implementation can be checked via my extended branch

BR Helmut

[Potherca]

The code changes look good. I haven't checked the www.plantuml.com/plantuml/ diagrams this time, though.

[kirchsth]

@Potherca: on plantuml server it is working (it overlays png with maps, details see end of #72).

[adrianvlupu]

Considering the changes, I think a new version needs to be released before merging this

[Potherca]

@adrianvlupu I've taken the liberty of tagging v2.1.0. (and supplying milestones for all MRs/issues) Do you think we should also create a release branch? (As was done with v2.0.0, since files now link to master).

[kirchsth]

@Potherca thank you for Release 2.1. Can you please release v 2.2 soon too?
(#126 contains following changes and therefore I think 2.1 should be a "short living" release:
UpdateSkinparamsAndLegendEntry -> UpdateElementStyle
SHOW_DYNAMIC_LEGEND -> SHOW_LEGEND
)

[Potherca]

@kirchsth Release is planned for my FOSS work this weekend.

[Potherca]

@kirchsth This has been released as v2.2.0.

Before tagging the release, I did add 621a191 and 34353dd to make sure that master doesn't break because of SHOW_DYNAMIC_LEGEND and UpdateSkinparamsAndLegendEntry being renamed. (This would have effectively meant a v3 release as it breaks backward compatibility). For future MRs this might be something to take into account, as we want to break master as little as we possibly can.

Obviously, we should have seen this when reviewing this MR, but beter late than never, right? 😁

I would have liked to add more to that release but, because of 2 reviewers being needed, things will have to wait for v2.3 . 😞

[kirchsth]

@Potherca thank you for the extension, deprecated is a good idea