Introduce a network-configuration object

[clhunsen]

Essentially, we should use two configuration objects:

• the project configuration, holding data paths, revisions etc. (right now CodefaceConf), and
• the network configuration, holding vertex and edge configuration details (i.e., artifact types etc.), edge and vertex attributes, ... (right now passed as repetitive method parameters).

This way, we are able to initialize data objects by just replacing the network configuration and remove tons of delegated attributes to almost all data-object methods. Additionally, the configuration just need to be done once -- by passing the configuration object to the constructor.

The list of network configuration options should be the following, at least:

• vertices and vertex attributes,
• edges and edge attributes,
• vertex relations for all parts of the networks ("mail", "cochange", "callgraph"),
• synchronicity data (yes or no), synchronicity time-window,
• directedness (see issue Distinguish directedness of networks and edge-construction algorithm #6 on this),
• network simplification (contract edges: yes or no),
• network-construction details (naming not fixed):
  • filter.artifact (only the exact artifact, e.g., filter feature expressions when using features as artifacts) [default: yes],
  • artifact.filter.base (remove BASE_FEATURE and FILE_LEVEL) [default: yes],
  • artifact.filter.empty (remove the "empty" artifact, i.e., remove all commits which does not changed a tracked artifact),
• skip.threshold from function construct.dependency.network.from.list,
• ...

Of course, all possibilites should be documented properly.

[clhunsen]

See pull request #20.