BUG: Ensure that data_frequency set on algo is set on sim_params.

Set the data_frequency member of an algorithm on the sim_params
configuration object.

Though the extra setting is slightly redundant, it is needed to
ensure that the same data_frequency is used throughout.

Should fix a bug where an algo that was intended to be run in minute
mode was operating as if it were daily in performance.

Possible TODO: Remove data_frequency as a param to TradingAlgorithm,
in favor of only being a property of sim_params.