Add a picture in Tripal home page

• add the parameter picture_path in the description section of the species in the input yaml, with the path to a picture : {{ org_param_desc_picture_path }}: {{ org_param_desc_picture_path_value }}
• add species.jpg or species.png in the species dir, taken from the previous parameter: take the picture of the "main_species" if available, otherwise the picture of the other species
• add a volume in the tripal service in docker-compose.yml : - ./species.png:/var/www/html/species.png:ro or - ./species.jpg:/var/www/html/species.jpg:ro