HBASE-23315 Miscellaneous HBCK Report page cleanup
* Add a bit of javadoc around SerialReplicationChecker.
* Miniscule edit to the profiler jsp page and then a bit of doc on how to make it work that might help.
* Add some detail if NPE getting BitSetNode to help w/ debug.
* Change HbckChore to log region names instead of encoded names; helps doing diagnostics; can take region name and query in shell to find out all about the region according to hbase:meta.
* Add some fix-it help inline in the HBCK Report page – how to fix.
* Add counts in procedures page so can see if making progress; move listing of WALs to end of the page.