Simplify Dataflow Tests

[bjthehun]

Closes #158, when merged.

• Introduces a DataflowGraphBuilder.
• The builder has convenience methods to easily add vertices/edges of a given type.
• These methods replace addVertex/addEdge in dataflow tests.
• Also removed default/optional parameters.

[EagleoutIce]

Looks great so far!

Hopefully, I will be able to take a closer look in roughly 12-14 hours!

Thank you very much for your great work!

[EagleoutIce]

I had some time to review the current changes :)

Thank you very much!

[EagleoutIce]

Thank you for switching to the builder layer!

[bjthehun]

Dataflow graph building itself has been simplified. However, defining/using references and environments still is comparatively cumbersome.
I'd probably wait for the code review, plus #673, to work on that, because inconsistent spacing gave me quite some trouble while switching to the builder methods.

[EagleoutIce]

I was not able to find an error in the updated tests!

[EagleoutIce]

I have just implemented #673.

@bjthehun Do you want me to handle all the new conflicts resulting from the unified spacing?

[bjthehun]

I have just implemented #673.

@bjthehun Do you want me to handle all the new conflicts resulting from the unified spacing?

If you want to, then yes.

[EagleoutIce]

This pull request is included in v1.4.2 (see Release v1.4.2 (Dropping xmlparsedata, Benchmark Re-Runs, and Repl Fixes)).

[EagleoutIce]

This pull request is included in v1.4.2 (see Release v1.4.2 (Dropping xmlparsedata, Benchmark Re-Runs, and Repl Fixes)).