Support further attributes on animals

[brookingcharlie]

Currently, we have limited information about animals: just name, description, species, and technical information about transmitters. To support more thorough description of animals, we'd need to extend the data model to include an animals sex, birth date, etc.

Also, if projects were to have hundreds of animals, the current user interface approach of having checkboxes to show/hide animals is no longer feasible. Filtering on particular attributes would be required.

It might be a good idea to make an animal attributes feature generic, i.e. instead of hard-coding specific attributes like sex, provide a generic facility to create attributes by name and data type. For example, the SOCPROG series of MATLAB programs for analysis of animal social structure supports arbitrary categories.