Change advanced-search button, mod error messages.

Add:
        templates/index.html, static/sass/index.sass,
        static/img/index/search_bar_magnifying_glass.png
                -Replace the magnifying-glass advanced-search icon with a simple
                textual button.

        static/(js/index.js, sass/index.sass)
                -Slightly modify the appearance of error messages; add message
                for no results.