Thread.addStackLine(): Return true on consumed line

And false if the line could not be consumed.
Thread._analyze(): keep track of unparsable lines
Add an Analyzer.toUnparsablesString() method

It returns a string we can show the user listing the input lines we
failed to parse.
Print the unparsable lines on the web page

Now they are just printed from top to bottom. We still need to:
* filter out empty lines
* count identical lines
* print multiple identical lines only once prefixed by their count
* sort the lines by count.
Ignore empty lines

As in "don't list them in the problems section at the bottom of the
page".

Also call the unparsed lines section "Ignored" rather than "Lines we
failed to parse".

"Failure" indicated there was a problem, while the truth might just as
well be that we're looking at an unimplemented already-planned
feature, or that it's just junk at the start or end of the thread
dump.
Show most common ignored lines first

Add a count before each ignored line.
Ignored lines: Use alphabet as secondary sort key

This way similar ignored lines will tend to end up close together.
Add list-ignored-lines test
Automatically focus text box on page load
Refer to TODO at top of the Ignored lines section

The point is that there are already plans for some of the ignored lines,
and getting bug reports for those won't help.
README.md: Done: List unparsed lines in red at end
Merge branch 'show-parser-problems' into gh-pages