Fix simpleDuration, modifiedDuration and convexity with Act/Act(ISMA)

http://sourceforge.net/p/quantlib/bugs/162/

This commit fixes simpleduration, duration and convexity with
Act/Act(ISMA)
Changed name of ignored file.
Merge pull request #28 from Nick Glass.

Fixed yield-based duration calculations for some day counters.
Merge remote-tracking branch: upstream/master