CRM-13075 - jobtabapp - Indicate which job is primary
CRM-13075 - jobtabapp - Add checkbox for is_primary
CRM-13075: is_primary UX

 * Set default value for is_primary on new jobs.
 * Disable is_primary checkbox if this is/will-be the only job.
CRM-13075 - Manually rerender is_primary (because it doesn't use mbind)
CRM-13075 - api/v3/HRJob - Maintain is_primary
CRM-13075 - Don't allow untoggling the primary
CRM-13075 - is_primary UX:
 * Hide checkbox when there's only one job
 * Fully refresh list view after changing general properties (like is_primary)
CRM-13075 - Sort jobs on is_primary. Rerender job list after collection reloads.
Merge pull request #75 from civicrm/master-isprimary

CRM-13075 - jobtabapp - Display/edit/use is_primary field