Add trade history levelDB, trade_MP call, clean up MetaDex populateRPCTransactionObject

1) gettransaction_MP now works for any metadex order not just open ones
2) populateRPCTransactionObject now parses off the wire for metadex just like all other types
3) new levelDB MP_tradelist
4) every *completed* trade added to tradelistDB with txids, addresses, properties, and amounts
5) new gettrade_MP call added
6) gettrade_MP will iter metadex map to determine if offer still active
7) new getMatchedTrades function added using tradelistDB to return all trades matched with a supplied txid
8) gettrade_MP will call getMatchedTrades and supply to user over RPC
9) mscrpc 7 function to dump tradelistDB

example
http://pastie.org/pastes/9698921/text?key=a5n5cqglbd80c7tfytwgxw
Difficult to end all iterations, but adding `break;` would end the most inner one. Another idea: set all iterators to the end, once found:

```c++
it_prices = prices.end();
it_indexes = indexes.end();
it_properties = metadex.end();
```