SEU scan integration

This merge request aims at integrating some scripts developed for SEU testing, put in the scans/seu directory.

Some changes in the central system interface libraires are included to allow for some running in continuous loops of scans and for bookkeeping of errors. In particular an __exit__ function is added in fifo_readout.py to prevent the number of threads to grow, while run_post_scans, run_analyze and use_raw_h5 arguments are added in scan_base.py to avoid interference with the closure of .h5 files called otherwise.