From File fails if "Hx" is the pause or stop motor

[padraic-shafer]

"From File" scans such as the Trajectory Scan allows a motor to be set upon pause, stop, or completion of the scan. New data files record this motor name in the header immediately after the "From File" line and before the line containing the scan file path.

als.bcs currently works correctly when this motor is "All Magnets" but not for other motors, such as "Hx".

At a minimum, the scans.get_scan_file_path() function should check for "Hx", but a more robust solution that allows any motor would be better.

[padraic-shafer]

ingest.get_data_file_header() assumes that the format is always:

From File
<pause-stop-motor-name>
<scan-file-path>

scans.get_scan_file_path() should do the same.

[padraic-shafer]

Created branch feature/0004/extract-scan-file.