fix doxygen warnings
Add instantations for class RungeKutta.
Fix copyright years in doc/users/doxygen.html

The year 2013 is already included in the range 2012 - 2014.
Added clear_current_row to TableHandler incase the current time step is rejected.
Revert "fix doxygen warnings"

This reverts commit 7cef480bb00c3a3de4c23da2486ef7487ee34de2.