Fixes for parameter file value lists

[breen0074]

Description

The changes here are intended to help address two different issues surrounding bids_import and parameter files.

• When importing parameter_file values that are a list, do not convert the entire list to a string before join(d57969b75875284e69b9f39cd27f5c66f87e768d). This ensures that the list is joined correctly instead of creating a list of every character from the original value.
• Check to ensure parameter_file is not empty before attempting to make any changes to int, or float lists(c5b411d0614b08d23367465fbaea0f8e7301eaf6). This prevents the bids_import.py script from failing if a parameter value contains an empty list.

[breen0074]

Closing to create a new pull request to the proper branch per request.