Check @-codes

Check @-codes by running a Python script.

All page files with notes must contain equal numbers of note anchors and note texts codes. In the OCR process, operators mark both using at codes. We check pages for equal numbers by running note_counts.py. The script asks which edition and which section. After checking all files, it outputs a list of differences it discovered, which must be manually corrected, or it prints the message section: @-codes match in all files.