Added a bunch of instance and class methods to CoinJar::Transaction to assist with separating out the different transaction types and some convenience methods on CoinJar which delegate to those methods, and also added a couple of methods to find transactions by their bitcoin txid.
Performance improvement: doing only one select is likely more efficient than two.
Fixed CoinJar::Address.list as per CoinJar::Transaction.list.
Merge branch 'address_list_fix'