add a 'repair' button on the webapi checker results page

[warner]

The "Repair" button appears when the checker results indicate an unhealthy file. But the target URL that it points at is wrong, so clicking on it doesn't do anything.

[zooko]

I'm going to find and comment-out the Repair button on the check-results-page for 1.4.0, then move this ticket ahead to Milestone 1.4.1. If someone else comments-out that button or otherwise fixes this before I get around to that (likely late tonight or tomorrow morning) then that's cool.

[warner]

I'll get it.

[warner]

code patched.. the button is commented out.

I think the bug might be related to files vs directories: the URL of the check-results page will look like FILECAP?t=check for files, and DIRCAP/?t=check for directories, so the relative link to the repair URL needs to be different (FILECAP?t=check&repair=true for files, and just ?t=check&repair=true for directories). Or, we should point directly at /uri/CAP?t=check for both, instead of trying to use a relative link. Well, except that we always want some kind of relative link, otherwise things break when you've got a proxy in front of the webapi server.

[zooko]

The button is comment out, and I'm moving this ticket to Milestone 1.4.1.

[zooko]

I think this is a new feature rather than a bugfix (since the button is absent, rather than broken, in v1.6.0).