Add transaction type Consolidated Send

List of additions:

* Added transaction type 7, Consolidated Send, a method of transferring all coins from all inputs to a single reference address.

This pull request primarily intends to increase the mobility of Mastercoin and derivative coins/tokens. The Consolidated Send transaction type attempts to emulate the functionality that the "change" output serves in a typical Bitcoin transaction - it consolidates all coins from the input addresses and makes them accessible from a single address. When used in conjunction with a Multi Send, pull request here: https://github.com/mastercoin-MSC/spec/pull/207, the cost (in Bitcoin and byte) per recipient can be reduced from that currently imposed by the Simple Send transaction type.