common internal model for issues in PR

[mildis]

Hi,

We are working on integrating Gerrit on the pr-decoration branch.
What we observed is that whatever backend is used for PR, there is a need for the same basic datas.
Of course, depending on the tool, some additional informations may be useful.

What about creating a common internal model for issues decorated in PR ?

• a PR message : the comment set in the tool timeline, a general message about the decoration
• file-wide issue : not specifically related to a line or range, along its severity
• 0 or more line-issue : issues that are bound to a line in a file (or a range of lines), along there severities too

[mc1arke]

This should now be included in #30 through the AnalysisDetails class. Let me know if you need more added.