Refactoring Checker statistics page

[csordasmarton]

Closes #1684

Add Detection status, Review status and Severity level filters to the statistics page.

[gyorb]

I think we should discuss this feature a bit more. Review status filtering can produce some interesting results.

All reports 14
unreviewed 4
confirmed 10
intentional 1

deadcode.DeadStores |   | 14 |   | 4 | 10 |   | 1

Actually there are 15 results but because the intentional filter is turned off the all reports column count will be counted by that filter even if the table shows the review status for all the reports.

[dkrupp]

We should not make selectable for a filter that is represented in a column.
So I think we should introduce the detection status filter with default value: new, reopened, unresolved and remove the "resolved" column from the table.

[dkrupp]

Please remove the Resolved column and add a new "detection status filter".
As a general rule of thumb, do not add a filter, which has a column in the table.

So do not add review status filter.

[dkrupp]

Do not add the review status filter as it appears as column in the statistics table.

Remove the "Resolved" column from the table and add the "detection status" as a filter among the filters.
This way one can show the distribution of the review status for the "currently outstanding" or for the "fixed bugs".