NeuralynxRawIO - keep_original_times inconsistent

[PeterNSteinmetz]

Describe the bug
The operation of the keep_original_times argument is inconsistent between different types of timestamps.

Additional context
At present, keep_original_times=True is setting the global_t_start to 0, amongst other actions.

I would expect this flag to work in the following way:

When False, all timestamps returned are relative to a global_t_start of 0, including spike and event timestamps and segment boundaries.

When True, global_t_start is equal to the earliest timestamp in any of the files parsed, whatever their type, and global_t_stop is equal to the last sample or timestamp in any file. All timestamps are returned with their original values and on the same scale as global_t_start.

This issue was exposed in Issue #1597 .

[PeterNSteinmetz]

It turns out this was not an issue in the code actually. Added a test to demonstrate how this works to test_NeuralynxRawIO in PR#1600 . Closing.