add norm_1(), norm_2(), norm_p() and norm_max() in VectorNorms.h. remove normEuklid().
add MathLib/Nonlinear in CMake
add NlErrorAbsDxNorm1
add NlErrorRelDxNormInf
add NlConvergenceChecker
add Picard nonlinear solver
add tests for Picard
remove constructor delegation
use spaces for index
rename "nr" to "picard"
add comment to Example1
use operator() instead of eval().
change eval() to operator() in examples
add namespace Nonlinear and delete prefix "nl" from file and class names
add prefix MATHLIB_NONLINEAR_ to include guards to avoid dubplicated macro definitions
rename "Dx" to "DeltaX"