Add folder location of stim file to assignments.xlsx (working but slow)

[nohelix]

Issue

Auto-picker needs folder location of desired stim file.

Expected Behavior

Create a new column called stim_location in assignments.xlsx that points at the desired file in Z:\Stim Files.

Notes

This will eventually negate the need for the "Changed" column.

[nohelix]

Ideas to improve the slow down by not dymanically search all the stim files each time

1. have a source list rebuilt when new files are made as filtering a table is fast
2. only look for files that have changed rather than all files