SAK-23179 update purepoms parent to 2.8.7

git-svn-id: https://source.sakaiproject.org/svn/jobscheduler/branches/jobscheduler-2.8.x@119057 66ffb92e-73f9-0310-93c1-f5514f145a0a
[maven-release-plugin] prepare release scheduler-2.8.4

git-svn-id: https://source.sakaiproject.org/svn/jobscheduler/branches/jobscheduler-2.8.x@119058 66ffb92e-73f9-0310-93c1-f5514f145a0a
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://source.sakaiproject.org/svn/jobscheduler/branches/jobscheduler-2.8.x@119060 66ffb92e-73f9-0310-93c1-f5514f145a0a