Error correction work in data

[murraycutforth]

This issue is to keep track of data issues which need to be dealt with.

In the course of the database creation work, I've found two issues, which are automatically handled using code in chlamy-ImPi/database_creation/error_correction.py.

1. Every single image sequence (stack of images in the tif file) has the first two frames repeated at the start. This is separate to the blank frames which are sometimes inserted.
2. Occasionally there is a random failed measurement, where a line is inserted into the csv with FM' all equal to zero, and a single F image is inserted into the tif.

[murraycutforth]

Also #16