Added smart property fundraisers, improvements to other future features

Also various cleanup and clarifications
Clarification requested by Marv
Added best practices for handling bitcoin reorgs
How to handle transaction version numbers
Better summary of how to handle version 0 sell offers
Some of the changes needed after reading Marv's comments about my pull request
More changes from Marv's comments
More changes from Marv's comments
More changes from Marv's comments
Adding a general purpose data field which can be used to store contract hash for a property (proof of existence)
Merge pull request #52 from dacoinminster/master

Added smart property fundraisers, improvements to other future features
Changes from pull request #46 which need to be merged in
Merge branch 'master' of https://github.com/mastercoin-MSC/spec
Merge pull request #57 from dacoinminster/master

We already approved this awhile back under PR #46, but that one couldn't be merged automatically, so I created this one.
clarified tx 20 behavior
updated version to 0.4.5.1
Merge pull request #59 from marv-engine/sell_offer_fix

clarified tx 20 behavior re: available balance vs reserved, committed, escrowed
We've decided (in the dev mailing list) to not allow the buyer to purchase more btc than they reserved.

That is, overpayments are now simply lost bitcoins, rather than trying to write logic to determine if there are some unreserved coins for sale that the buyer could have in exchange for their overpayment.

Keeping it simple!
Merge pull request #60 from dacoinminster/master

We've decided (in the dev mailing list) to not allow the buyer to purcha...