Summary report for unique errors

[sveetch]

When using report on huge site and it can become hard to make an inventory of all error kinds since you need to crawl on every page report with error to collect each unique error kind.

Like on 500pages which report a total of 200 errors, you may have 80 ones which have invalid link closing tag, 60 errors about missing "alt' attribute on image, and a 5 other various errors.

Finally, you have 7 different errors kinds you may fix quickly but it is hard to know without to read for 200 errors.

There should be a summary of unique similar error based on the error title, not the content.

[sveetch]

Also, the report index should have better readability to distinguish errors on huge page list with something more visible like in the page report detail or even better, some Javascript/CSS for a feature to filter for error only, warning only or both.