Fix links to doc/reports/index.html.

This file (lost in the conversion from svn to git) was moved to http://www.dealii.org/reports.html since the actual reports are already there. This patch redirects the links there as well.
Merge pull request #30 from bangerth/move-reports-master

Wolfgang. This file (lost in the conversion from svn to git) was moved to http://www.dealii.org/reports.html since the actual reports are already there. This patch redirects the links there as well.

Fix links to doc/reports/index.html.