Evalai: Add support editing a challenge details on UI

[deshraj]

Current Status

Currently, we have all the APIs required for editing the challenge. UI needs to be implemented so that the challenge hosts can edit the challenge on their own.

Deliverables

Note: There is a constraint that only challenge host should be able to edit the details on the frontend and hence the edit buttons should be avilable to the challenge hosts only.

1. Challenge host should be able to edit the following fields:
2. [x] Challenge name
3. [x] Challenge short description
4. [x] Challenge long description
5. [x] Terms and conditions
6. [x] submission guidelines
7. [ ] start date
8. [ ] end date

9. [x] evaluation script

10. For a challenge phase, following fields should be editable:

11. [ ] phase name
12. [ ] phase description
13. [ ] start date
14. [ ] end date
15. [ ] test_annotation file (Open a dialog box showing warning "Do you really want to do this? " Also, ask the host to enter the phase name here to make sure that he/she is not drunk while doing this)
16. [ ] max submisasions per day
17. [ ] max submissions

Note that this is a big issue and can be submitted as two different pull requests: one for editing the challenge details and the other for changing the challenge phase details. We want to add support for editing more meta details of the challenge and we would like to do that once we have these features in place.

[RishabhJain2018]

@deshraj I would like to take lead on this.

[deshraj]

Sure. Assigning it to you.

[RishabhJain2018]

@deshraj Please take a look at the UI.

[deshraj]

Challenge description will be really long so it would be nice if you can increase the width and height of the dialog box. Rest this looks good to me.

[RishabhJain2018]

Currently, I am doing the First part(Editing Challenge) of the issue, the second part is still open to everyone, as we will have two PR's for the same issue.
Please make the UI as shown in the above comment.
Let me know if there is any problem.