Read NWB date_of_acquisition from the stimulus pickle file

[danielsf]

As discussed in #2412 the date_of_acquisition values recorded in LIMS do not agree with the start_time recorded in the stimulus pickle file. Because we want our dates of acquisition to agree across sessions and metadata tables, we are going to take date_of_acquisition form pickle_file_data['start_time'] to be maximally self-consistent. This means either

1. modifying the input.json files used to produce NWB files so that they get date_of_acquisition from the pickle file
2. modifying NWB generation so that it ignores the date_of_acquisition in the input.json and just reads whatever is in the pickle file.

If we go with (1), I think we should take on #2400, understanding that the LIMS querying methods implemented in #2407 should make that much easier.

Validation

• When NWBs are generated, date_of_acquisition should agree with what is recorded in the stimulus pickle file.

[danielsf]

Might be redundant with #2400, which should allow us to write the correct date_of_acquisition to the input JSON file.