Retina move to a new module : bioinspired

Creating a new module (following discussion with Vadim).

=> new module : bioinspired. the aim is to place inside algorithm/models based on biological models

=> Retina class has been moved there as a first member

=> Retina is now included in its own sub namespace cv::hvstools. Other classes using the same namespace will be added later.

=> Retina interface now has a new method that allows fast tone mapping (adaptation of Meylan2007 work)

=> all documentation and tutorials have been updated following the changes