Better save for jobs panel

[taylordowns2000]

1. When creating a new job, the "Save" button should say "Create" rather than save because the record is not stored until the button is pressed. This will help with a current UX frustration where users cannot tell if they are creating a new job or editing an existing one.
2. As anyone, I'd like to be able to save my changes to a job without closing the jobs panel. (Having the panel close is particularly frustrating when I'm first building a job, as certain features are blocked until the job is saved.)
3. As a developer-user, I'd like command-s or control-s to save my job expression and not close the panel.
4. The "cancel" button should instead say "close" and if I attempt to close or click away with unsaved changes I should get a warning indicating that i have unsaved changes.

[taylordowns2000]

@amberrignell , @mtuchi , i'm moving the "warn on unsaved changes" bit here (see x-ed out item 4 above) into a new issue: #780