Experiment tracking

[Oxid15]

Adds new field to enhance tracking of environment:
Each model that was saved with the line will now have:

• Hostname
• Username
• Latest commit hash if cwd is inside a git repo
• If hash is present
  • current working directory
• full python version
• names of files that are not currently committed if inside git repo

All git capabilities work using actual git and relies on its presence in the system. If the git commands will not run, those fields simply will not be included.