Renaming data folders

[TomazErjavec]

Currently the samples are in the Data/ directory, while the complete corpora (which are, however, gitignored) are under the Distro/ directory. Neither of these names is really appropriate, so the suggestion is to:

• rename Data/ to Samples/
• rename Distro/ to Corpora/

The renaming is simple enough but this also means that:

• Makefile has to be changed to reflect the new names of directories
• The partners have to be notified of this change

[TomazErjavec]

I think this has been sorted now.