Update and enhance README file(s)

[bockthom]

• (1) I just noticed that our README file still points to the already archived version of siemens/codeface.
  I suggest to replace the outdated pointer by a link to se-sic/codeface (but adding a comment that codeface was originally developed by Siemens).

• (2) In addition, it might be useful to state which data of the main data sources (commits, mails, issues) can be extracted by which tool (e.g., by adding a link to the respective tool, such as codeface or GitHubWrapper). However, I am not sure where to add this information. As coronet relies on codeface-extraction instead of directly using the outcomes of the different tools, maybe the README of codeface-extraction would be more suited to that, and we can just point to the codeface-extraction in the README of coronet for further reading upon how to extract data from the different main data sources.

@hechtlC: What do you think?

I would like to fix part (1) ASAP; part (2) is not as urgent.

[bockthom]

I've already addressed the first part of this issue right now: outdated pointers to siemens/codeface are replaced by se-sic/codeface now.

Regarding the second part of this issue, @hechtlC and I agreed that coronet should be independent of the data sources and tools via which issue or mail data have been extracted. Therefore, we won't add any information to the README that points to specific extraction tools. Instead, providing information on these tools could be added to the README of the codeface-extraction project. If we add such information on tools there, we can add a single sentence to the README of coronet, stating that further information about potential tools can be extracted from the codeface-extraction.