output (optionally) the name and version of used addins

When Cake has compiled the build.cake file it might be useful to output the names and versions of the used addin's for diagnostic reasons.

Start by tracing how Cake compiles build.cake and tracks the addins used during that process. Identify the existing diagnostic or output path and determine how optional addin names and versions would fit there. Done means the requested information can be output optionally without changing the default output.

Written by the indexing model from the issue text.