lib: moves the file::files method from the nitni to the ffi format

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitdoc: adds suffix to class names in generated dot code to avoid conflicts

Previously, the some class names (Graph and the like) were in conflict with
Dot keywords.

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
fix dirty commit

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>