Added metrics on abstract view

The abstract view now has an 'Analyze' dropdown menu. This contains a new function 'render_abstract_analyze_menu', which in turn uses a new function 'single_metrics' in 'record_list_functions.js'. This function grabs the bibcode in the hidden input box (with bibcode value 'selected') in the abstract page. So, essentially, the existing 'metrics' function could be used, but this way we have flexibility to change this down the line.