Rewrite Analyser.toString()

Split it into one part that lists threads with stacktraces, and one
part that turns that into a string representation.

This is a first step towards turning the analysis part of the web page
into HTML.

Fails one test though, needs debugging.
Make multiline test diff more readable
TODO: List top RUNNING methods first
Improve unit test string diffs

Validate full analysis test output vs an array of lines rather than a
big string. This makes empty lines properly highlighted on the results
web page.
Add more analysis tests
Test that we sort threads by name when analysing
Drop superfluous newline at end of analysis
Make the Analyzer sort threads by header contents
Merge pull request #3 from spotify/rewrite-analysis-tostring

Rewrite Analysis.toString()