Fix TrilinosWrappers::SparseMatrix::add(factor, other_matrix).
Merge pull request #168 from kronbichler/master

Fix TrilinosWrappers::SparseMatrix::add(factor, other_matrix).
Remove stray Id tag from svn from all headers
Merge pull request #169 from kronbichler/master

Remove stray Id tag from svn from all headers
Patch suggested by Xinzeng Feng <xf39@cornell.edu>: Fix a mistake in a code example.
Merge pull request #170 from bangerth/fix-formula

Patch suggested by Xinzeng Feng <xf39@cornell.edu>: Fix a mistake in a code example.