Fix errors due to misplaced `read_data.py` and NionSwift 16.2

Created by: francisco-dlp

In my installation, using Nion Swift 16.2, I need the fixes in this PR to run the plugin.

In particular:

• The path of the read_data.py file was wrong
• In NS 16.2, frame_parameters is not a dict, so things like if "acquisition_mode" in frame_parameters: don't work.