nitdoc: Adding functions in MPropDef

Added one functions to set the text color in terms of the visibility of
the property, and another to get the full path of the property at the
right norm

Signed-off-by: Stefan Lage <lagestfan@gmail.com>
nitdoc: Cleaning ReadModule class

Signed-off-by: Stefan Lage <lagestfan@gmail.com>