Add new configuration files for ceilometer

According to patch: https://review.openstack.org/#/c/77957/, and patch:
https://review.openstack.org/#/c/42713/15, new configuration files named
api_paste.ini and event_definitions.yaml are introduced, this patch
adds them to ceilometer configuration directory.

Change-Id: I57165d588da35f13b2d22629b48dc087502598a7
Merge "Add new configuration files for ceilometer"