This commit:
1) Adds anchor peers upon channel creation
2) Extracts them at the peer side in the gossip layer
   and uses them.
3) Changes an internal API of a method in gossip
   from GetTimestamp to SequenceNumber, because
   using sequence numbers is better than using
   timestamps, that are machine-specific in
   contrast to sequence numbers which are global.

Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>
Change-Id: Id080585a56a5083d9cd4911ce790e5be389cfa52