Read and write data arrays of type std::size_t under linux and windows in the vtu io.

This makes it possible to read and write std::size_t under linux and windows.

Enabled Eigen preconditioner configuration

[MGTL] Deep copy of seg to avoid modifying orig. pnts.

Added flexible nonlinear solver convergence criteria

add a CLI tool flipNodeCoordinates

New tool convertGEO and some minor fixes

[scr] fixed format() for python 2.6 compatibilty