Counts per error kind

[pgorod]

Feature request:

The final report at the end of execution currently has this aspect:

========================================================================
✘✘✘ failed in 1.46113043s
260 errors in 225 documents

To facilitate working through large numbers of errors, it would be nice to see something like this instead:

========================================================================
✘✘✘ failed in 1.46113043s
180 "target does not exist" errors in 145 documents
80  "hash does not exist" errors in 80 documents
------------------------------------------------------------------------
Total 260 errors in 225 documents

Thanks

[pgorod]

Emulating this feature in bash:

./bin/htmltest  | tee >(grep -v 'errors in\|failed in\|htmltest started\|======' | cut -d '-' -f 1 | sort | uniq -c -w 10)