Homogeneize coding style.

  - TypeWkPtr -> TypeWkPtr_t.
Add accessors for maxIterations and errorThreshold

  in classes ConfigProjector and ProblemSolver.
Add a local map of numerical constraints in ProblemSolver

  - numerical constraints are stored by name in a local map in order to be
    inserted into the ConfigProjector.
Merge branch 'master' of https://github.com/florent-lamiraux/hpp-core