Transformation from v1 to v1.6

Adds a `rake` task to transform files in v1 format to v1.6. (run `rake -T` to see the exact name of the command). It takes all files present in the v1 folder and creates new transformed version of them in a v1.6 folder.

Note that the [transformer](http://github.com/LFDM/treebank-transform) tries to add CTS information inside the documents and tries to adapt the file name according to it. This doesn't work yet for all files.