[TW-156] Burndown report should take as parameters start (and perhaps end) dates

_Cory Donnelly on 2011-05-16T18:53:58Z says:_

The current burndown report allows a user to specify how granular to make the report (daily/weekly/monthly) and filter report contents using tags, etc., but there is no way to limit how far back in time to go.

In my work environment we use three week sprints -- it would be nice to be able to generate a burndown.daily report that starts on day 0 of the current iteration.