List of architecture changes:

- removed submitting peer. Modified Section 2 to convey this.
- added an option to optionally "anchor" the execution at endorsing peer
- modified endorsement policies section to say that chaincode refers to
  pre-built end. policies
- removed confidentiality section

Change-Id: Ibfa3bfe2f696110a375b4b54f8057f2f9be146ba
Signed-off-by: Marko Vukolic <mvu@zurich.ibm.com>

Author: Marko Vukolic