Add species as a request parameter for metadata search endpoint

[alfonsomunozpomer]

I added a request parameter to both the JSON and the view/HTML controller. The service and DAO classes that are called from the JSON endpoint have now two methods to search with/without a species. The HTML controller, in turn, passes the parameter as a prop to the React component. The React comopnent needs to be aware of this prop in a following story.

[alfonsomunozpomer]

@ke4 Please have another look. I reworked the controller/service/DAO classes to delay the optional behaviour all the way to the DAO class, so we don’t have overloaded methods. Initially I thought this was clearer in terms of intent, but maybe this is clearer and easier to read.