XLS output for grid.

[Jérôme]

Dear all, 

I have implemented an XLS output for musical grids, so as to export them into speadsheets before weak or strong compression.
This is useful to debug and to better understand how story compression works. 

Unfortunately, the XLS encoding does not exploit the sparseness of the grid, so it will not scale to big stories. 

This is a developer only feature that can be activated in the code only by tuning the two following booleans: 

  let dump_grid_before_weak_compression = false

  let dump_grid_before_strong_compression = false 

in 

  cflow/compression_main.ml 

Best wishes.
Jerome.