Make dpu compatible with re-launching experiments through app.

[ezirayw]

What? Why?

Ensures that dpu can enable re-launching of experiments continue without overriding data.

Changes proposed in this pull request:

• Introduce additional flag when initializing experiment to differentiate between new experiments and recovered ones

Checks

• Updated documentation.
• Follows 7 rules of great commit messages. For most PRs a single commit should suffice, in some cases multiple topical commits can be useful. During review it is ok to see tiny commits (e.g. Fix reviewer comments), but right before the code gets merged to master or rc branch, any such commits should be squashed since they are useless to the other developers. Definitely avoid merge commits, use rebase instead.
• Follows the Google Style Guide.

Any screenshots or GIFs?

[zheins]

Can this be closed? I don't think it's needed anymore.