Introduction of implementation characteristics/tags

[rbergen]

This PR is drafted to initiate the introduction of defined implementation characteristics. The following is used as a premise:

• The substance of issue Discuss how to report on alternate algorithms #177.
• Conversation I've had with @davepl over the past number of weeks.

I'm opening this PR as a draft, for now. The reason is that I think we should first be fully aligned on the contents of the contribution guidelines related to the specification of characteristics, before we start making changes to existing solutions to make them conform to the new setup.

[rbergen]

I've continued adding labels to existing solutions, and just pushed the changes up to and including PrimeJulia. I implemented but stashed the changes for PrimeCSharp/solution_1, as a proper addition of the labels to that solution requires a different set of changes than just a literal text change to (the) drag-race output line(s). I'll compose a separate PR for that solution (after this PR is merged), that I would like to then receive a review on from @Kinematics, if possible.

I'll keep working down the list of solutions over the next few days, and push again once I've reached the end of the list.

[rbergen]

All solutions except for one or two exceptions have now had the labels applied. I'm thus marking this PR ready for review. Obviously, we shouldn't merge until the benchmark implementation is updated to process the new output.

[mike-barber]

Wow, nice work!

[rbergen]

Wow, nice work!

Thank you! I'm sharing the credits with @marghidanu and @rhbvkleef, because it really took a coordinated effort to make the whole thing work, in the end. :)

[rbergen]

Going to merge this now that I've confirmed that the new benchmark tool report includes tags for all solutions except PrimeCSharp/solution_1, for which I will open a separate PR.