document Intercepters in ActionMailer guide
Merge pull request #8967 from senny/add_interceptor_to_am_doc

document Intercepters in ActionMailer guide
clear specific logs when using rake log:clear
Merge pull request #8964 from mattdbridges/specify-log-to-clear

Clear specific logs when using `rake log:clear`
Deprecate direct calls to AC::RecordIdentifier.dom_id and dom_class

Also add some generic tests to ensure they're properly deprecated.