Implement Textual report

[danglotb]

For now, Diff-JJoules can only build a report in markdown format (for commenting on pull-request on GitHub).

We should implement a new format of the report, the basic one is just a textual report.

One could be inspired by the implementation done in Markdown, but adapting the formating to have a nice report in a text file and in the console.

[danglotb]

• Interface Report
• Object that carries result to output
• Implement TextualReport