Always use the reduction of the maximum of the weighted residual as convergence criterion

This should make things a much more robust, partially because now the
linear and the non-linear solvers use the same convergence criterion.

Also, this patch includes some collateral indentation improvements.

examples/co2injection_pvs_vcfv.cpp

@@ -19,8 +19,8 @@
 /*!
  * \file
  *
- * \brief Test for the isothermal primary variable switching VCVF
- *discretization.
+ * \brief Test for the isothermal primary variable switching model using the VCVF
+ *        discretization.
  */
 #include "config.h"