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
Looks like a duplication of [mastercore_rpc.cpp#L1921-L1947](https://github.com/mastercoin-MSC/mastercore/blob/mscore-0.0.9/src/mastercore_rpc.cpp#L1921-L1947).

Maybe replace by something like:
```c++
void evaluatePopulationStatus(int nResult)
{
    switch (nResult) {
        case MP_TX_NOT_FOUND:
                throw ...
        ...
    }
}
```