[DOC] Using DIB for images / installation

* Docs for howto getting started with DIB
* Howto build Libra LBaaS elements using DIB

Change-Id: I776f64d11c8a75f8104208e60f13427c4f8fb5f8
[API] Move socket creation into libra.common.api and support not having SSL

Change-Id: I42d4f82f853d8eedccb5408e55a6924b09d04541
Merge "[API] Move socket creation into libra.common.api and support not having SSL"
Merge "[DOC] Using DIB for images / installation"