Adding persistence features

Adding persistence features
1) Feature Tests Pass: https://jenkins.opendaylight.org/releng/view/persistence/job/persistence-merge-master/45/
2) Features Comply with Guidelines: https://git.opendaylight.org/gerrit/#/c/22928/1/features/index/src/main/resources/features.xml
    a) Feature Names: Prefixed with 'odl-' : odl-persistence-api
    b) Features Descriptions: Present
    c) Features Start-Levels: No start-levels on <bundle> elements or <feature> elements
3) Features Tested: Features have been tested for functionality with
    a) feature:install odl-persistence-api
    b) feature:install odl-integration-all
4) Integration Test Impact- none

Change-Id: I620a6e1675e72a2887a44a3a76b5334e51dc7b1a
Signed-off-by: My Trinh <mydung.thi.trinh@hp.com>