Added new interface for mesh/contour handling

Added base code, just for computing node-to-node distanced.
Some other computations could be added here.
Fix: input_spec and output_spec were not set

Fixed bug in surface-to-surface distance computation.
Implementation of surface weighting

Also fixed total weight normalization
Fixed bug

Input parameter name was used wrongly
Merge remote-tracking branch 'origin/enh/MeshAlgorithm' into enh/MeshAlgorithm
Working version

Checked that works with vtk files. Also checked for consistency when
using the same surface twice.
Fixed tests
changelog
Merge branch 'enh/MeshAlgorithm'

Conflicts:
	CHANGES