Log dir

[carnisj]

Now the log file will be created in save_dir if this parameter is defined, otherwise in root_folder. This will allow the user to avoid permission issues in root_folder.

Modify the saturation threshold of the Eiger2M detector from 1e6 to 1e7 photons.

Fixes #261

• Bug fix (non-breaking change which fixes an issue)

Checks:

• I have added unit tests
• I updated the documentation
• I have run doit and all tasks have passed

[ccechatelier]

Sounds good to me !