allow for start and stop to be in any order

when making api requests from client side where two timestamps must be specified, I've noticed there is no standard as to which is first; start or stop.

If these were to be standardized; ie start always before stop it would break many apps already in use.

Ideally, either method would be acceptable and the two time stamps would be sorted on server end to be in appropriate order.

Example of two calls which require confusing opposite usage:

```
#python api call parameters

DB = '{"id":1,"method":"call","params":["database",'
HISTORY = '{"id":1,"method":"call","params":["history",'

get_market_history = (HISTORY + '"get_market_history",["%s","%s","%s","%s","%s"]]}' %
(asset_id, asset_id2, 14400, then, now))

get_trade_history = (DB + '"get_trade_history",["%s","%s","%s","%s","%s"]]}' %
(currency, asset, now, then, 100))
```

note now/then vs then/now

Start by tracing the get_market_history and get_trade_history API entry points in the server implementation and compare how each currently interprets its two timestamps. Verify the behavior for both timestamp orders, including the Python request examples, and add or update coverage so both calls accept either order consistently.

Written by the indexing model from the issue text.