Minor fixes for secondary index usage.

- Additions to UprEvent structure,
  UprStreamBegin, UprStreamEnd, VBuuid, OldValue
- renamed UprEvent:SeqNo to UprEvent:Seqno
- send reference to UprEvent instead of copying the structure into the
  channel.

Patchset 3:
- remove placeholder fields, UprStreamBegin, UprStreamEnd, VBuuid.

Change-Id: I1d3537164a75bbbc34fd011ffae23c619649bce3