Set seed for run

[mfeurer]

First try to do this: 23de78b

This commit won't be merged and should be redone.

[janvanrijn]

I authored a huuge pull request.

Summarizing the state:

• Users can upload unseeded flows (a random seed will be selected and uploaded to the server)
• Users can upload flows seeded with a int (will be uploaded to the server)
• Flows with a RandomState object are rejected (too hard to reproduce)

Having this functionality, we can also re-instantiate serialized flows and parameter settings on the server. I added this functionality, so we can test the seed function (and use run instantiation). Will add some more tests tomorrow and then it will be done, I suppose.

Furthermore, would be cool to have a feature to reinstantiate configurations based on parameter trace. Need to open an issue for this to review the state of this.

[mfeurer]

Was fixed in #241