[💡Feature Request] Specify date range for backtesting

[tfukaza]

Describe the feature Allow users to specify the date range of backtesting data. This is useful not only for users, but also for testing purposes, in order to limit the amount of data downloaded.

Interface BackTester.start() will take 2 new params:

• start: start date and time of backtest, in format "MM-DD-YYYY:HH:MM:SS", or "MAX" to use the max range.
• end: start date and time of backtest, in format "MM-DD-YYYY:HH:MM:SS", or "NOW" to use current time

Behavior If specified API class cannot supply all the data within range, an Exception should be raised.

[tfukaza]

This is marked as high priority as this feature is needed to test BackTester