Missing methods

Another pull request for missing bindings. 
This adds the methods `getTransaction`, `listTransactions` and `listAccounts`. It makes heavy modifications* and renames `SinceBlockTransaction` to `SimpleTransaction` and adds `DetailedTransaction` and `DetailTransactionDetails`.

\* *I had not tested the type with all categories of transaction, which turned out to be a mistake. These modifications should fix all the bugs involving its parsing.*