Add Appendix F - Concerning the Proposal for the Output Model

Appendix F includes details on the proposal for the Master Protocol to transition to an output model.

The section is incomplete and it's not my intention that this be merged immediately. I would like to use it as a place to discuss a potential plan for the transition to an output model, and to detail the benefits and mechanisms by which an output model would function. Note, this is section doesn't answer "should we transition," but what the transition would look like if it were to take place.

Notable items include:

- Proposal for drastic decrease in Master Protocol transaction costs (over 50% reduction)
- Atomic Meta DEx (which to my knowledge hasn't been done before with an output model)
- Notes on the use of Mastercoin in an output model
- Thin clients
- P2SH and multisig support
- Proposal to remove the required output to the Exodus address
- Proposal for cross protocol atomic swaps (interoperability with other protocols!!)

Relevant sources: 

- https://github.com/mastercoin-MSC/spec/issues/192 Reduce transaction costs
- https://github.com/mastercoin-MSC/spec/issues/189 Should we migrate to output model?
- https://github.com/mastercoin-MSC/spec/pull/233 Pull request for relevant whitepaper
- http://www.reddit.com/r/mastercoin/comments/2bz8ub/how_the_monetization_of_mastercoin_will_lead_to/ A post on the necessity for Mastercoin to change directions or face irrelevancy.