Added @layout annotation to add arbitrary layout options an elements

[soerendomroes]

This adds the @layout annotation to set arbitrary layout option supported by ELK.
All options for the layered algorithm and their corresponding values can be found here together with additional documentation.

I recommend trying out different options in the interactive elk-live editor if questions should arise. Otherwise, feel free to tag me if you have questions.

Layout options can be specified in the following pattern:
@layout(option=<elk-option-id>, value=<elk-option-value>)

E.g. if we want to set a port side, we can use the unique suffix as an option id for port side
.
The id is org.eclipse.elk.port.side, hence port.side will be unique. Depending on the option side may also be unique but it this case it collides with other option ids.

target C

reactor test (a:time(1 s)) {
    @layout(option="port.side", value="NORTH")
    output b: time
}

This should mainly be used for testing out different options, e.g. different layout directions, and for creating drawings for papers and documentation without the hassle of changing the synthesis.

[cmnrd]

Thanks! I think this will be helpful. I'll play around with this and see if it resolves some of the "issues" I had lately.

Could you run ./gradlew spottlessJavaApply to apply the code formatting and commit the changes? I would do it myself, but I don't think I can push to your fork.