Lut-based neighborhood sequence distance transform

Aim:
This code implements a distance transform for neighborhood sequence distances described in “Path-based distance with varying weights and neighborhood sequences,” Nicolas Normand, Robin Strand, Pierre Evenou and Aurore Arlicot in DGCI 2011.

The distance transform is computed in two steps:
- an asymmetric version of the distance transform is computed in a single raster scan of the image,
- the asymmetric distance transform is “untranslated” using semi-local operations, still from the top to the bottom of the image.

The neighborhood sequence can be defined as a periodic sequence when one period is given or by the use of a rational Beatty sequence.

The algorithms are pipe-lined and work as image filters, taking rows of the input image one by one and providing output in the same manner. The delay between input and output is minimal and the memory consumption is low (a few rows of image).

Status of the code:
This is a first port to DGtalTools and has some flaws such as:
- a total independence to distances as they are defined in DGtal,
- a pipe-line model (with image producers and consumers) not supported by DGtal,
- it has its own readers and writers,
- it probably redefines a few more things that already exist in DGtal.

The code is probably not ready to be merged into DGtalTools right now. Any comments and suggestions for improvement will be helpful.