Interpolation at points

Topics
	The point interpolation (generic) module
	The (generic) point interpolation module.
	Lagrange point interpolation
	Field interpolation and derivation to arbitrary points.

Modules
module	mod_point_interpolation_init
	Initialization of declared extrapolation chemes.

Detailed Description

This module is split in two, for backward compatibility:

1. Lagrange point interpolation (former version)
2. Generic point interpolation (with more diversity in schemes)

Todo:

MCO: do a proper integration of "Lagrange" point interpolation in the new framework. But before I need to test for efficiency matters.