Configurable commit message template

[lukaszwawrzyk]

Commit message for dependency update should be configurable with a template.
Default template would be "Update {dependency} to {versionTo}".
We may consider what variables for template will be provided. We could allow specifying group/artifact for maven deps separately for example.

Regardless of PR grouping, we will put each update in a separate commit so the commit will always be about single version update.