Implement a line search strategy to deal with cases where the nonlinear iteration...

Implement a line search strategy to deal with cases where the nonlinear iteration in MappingQ1::transform_real_to_unit_cell does not converge. If the line search doesn't converge either, then throw an exception and assume that in fact this means that the point lies outside. Deal with this result in all of the places where we call the function.

git-svn-id: https://svn.dealii.org/trunk@25651 0785d39b-7218-0410-832d-ea1e28bc413d