Allow marking reports as INVALID

[preaction]

Once we can authorize user accounts to given PAUSE IDs (#14) or tester e-mail addresses (#15), we can allow users to mark reports as invalid.

We should add page that allows searching for a report ID. Once the report is found, the user should be able to type in an explanation for why they are marking the report as invalid, and then hit submit. Once this happens:

1. If this is done by a distribution maintainer, an e-mail should be sent to the reporter with the explanation inside.
2. The test report grade field and the summary table state field should be set to INVALID.
3. The report should be removed from the release data
4. A field should be added to the test report, in the comments top-level hash, called invalid_description, which should contain the text of the explanation as to why this report was marked invalid.