Create two classes of d-g jobs.

Split d-g jobs into two classes. Those that run against proposed changes
and periodic jobs that run against the current state of a branch. Do
this to make expectations around new jobs clear and to make the addition
of post release jobs simple. After this change merges all d-g jobs
should come with both forms of job template.

Change-Id: I52beb1fa1df2ed06fa992792246f767ca9d4957d
Merge "Create two classes of d-g jobs."