Add support for new auditing API

Bitbucket 7 introduced a new cross-platform auditing API that offers some advantages over the existing (now deprecated) auditing API that ScriptRunner currently uses.

The main benefit of the new API is that it allows us to supply changed configuration values, which means we can show the detail of what has changed in the configuration in a more user friendly way, rather than showing a JSON string representing the changes.

Using the new API will also allow users to filter audit events to a ScriptRunner "category" so they can see all historical changes specific to ScriptRunner.