Remove the light blue line to the side of interacts

[jasongrout]

As Ondřej Čertík writes in a message to sage-devel:

• the blue line for interact (the server is computing) is not very
  intuitive for me, it took me a while to realize
  that this is what it means

I agree with him that it isn't very intuitive that the blue line is to distinguish nested interacts from each other. I think we should remove the blue line, and figure out something different (on another ticket).

[certik]

In fact, I got it wrong! I thought the blue line means that the server is computing. But it is there all the time. Oops.

[jasongrout]

Ah, so we could close this the other issue by repurposing the blue line to be what you think!

[certik]

Yes --- but I would suggest to use some clearly visible spinner or some text across the whole output saying "Evaluating" or something.

[jasongrout]

Fixed by gh-268