add presend-script to email-ext

Change-Id: I388dd2f5ce8aa6ac323f73409dec1003a3f423cb
Make 'keep_descriptions' fully optional

Avoid the need to set the keep_descriptions option under the job_builder
section if providing any configuration options.

Change-Id: I0436a36e9f5ad7ff68ff5b92868ca1b13d019f11
Merge "add presend-script to email-ext"
Merge "Make 'keep_descriptions' fully optional"