Adopt generic network functions from other projects

[clhunsen]

There are a bunch of functions from other projects that should be incorporated and adopted into this project.

Some functionalites that we should transfer here:

• discretization of project-level networks (time-based or activity-based)
• combination/addition of networks (see https://github.com/se-passau/dev-network-growth/blob/master/util.R#L64, Possibility to build cumulative ranges #61, Support multi-artifact networks #15, and Combine networks and provide multi-relation networks #98; PR Add multi-edges to the author and artifact networks #115)
• core/peripheral developers (also needed for Vertex attributes #34, added in PR Add core/peripheral classification functionality #51)
• universal network-construction function (see https://github.com/se-passau/dev-network-growth/pull/39)
• motif identification (see PR v2.2 #42)

[clhunsen]

• combination/addition of range-level networks (see https://github.com/se-passau/dev-network-growth/blob/master/util.R#L64 and Possibility to build cumulative ranges #61)

Do we still need this in the described form after the landing of PR #96 and, thus, the closing of issue #61?

[bockthom]

• combination/addition of range-level networks (see https://github.com/se-passau/dev-network-growth/blob/master/util.R#L64 and Possibility to build cumulative ranges #61)

Do we still need this in the described form after the landing of PR #96 and, thus, the closing of issue #61?

@clhunsen The closing of issue #61 enables to combine ranges and the respective data, but not to combine networks in general. Therefore, I have updated the initial comment and removed the word 'range-level'.

So, what we still need is a function to combine networks in general, which combine networks and keep edge types, node types, and possibly attributes. @ecklbarb is working on combining different kinds of networks, I guess. I will open an additional issue where we can keep track of the current progress and ideas.

[clhunsen]

I added the new information on the merging of networks to the opening post (essentially, #15 and #98; PR #115).