Misc release-beta edits

overview/contributing.rst
-------------------------
  o In section "Submitting Code", document jira ticket fields to
    populate and mention they are used for release notes.

howto/release/repositories/index.rst
howto/release/repositories/voltha-lib-go/release.rst
howto/release/repositories/voltha-onos/index.rst
----------------------------------------------------
  o Create stub topics for documenting branch/tag creation by repository.
  o Document external dependencies, build order, etc.

Change-Id: I4c4f2860c2ab9ba801972de147fd224669d6d428
1 file changed