[Amibe] Add singularity order 'alpha' for analytic metric
[Amibe] Cosmetics: update help on refine.py, remesh.py and remeshSingularity.py
[Amibe] Update example of RemeshMetric in python script for the cube model problem

Modify analytic metric for a singularity in 1/r^alpha
[Amibe] Add numerical criterion and mixed metric in class RemeshMetric
[Amibe] Simplify computation of numerical metric with linear interpolation
[Amibe] Numeric metric: geometric interpolation on first interval