History panel: allow searching datasets: name, tags, annotation, dbkey, file_ext, blurb, and info will be searched when enter is pressed in the search field, include whitespace by enclosing search term in double quotes, allow specifying which field to search by using the idiom 'field=term' where field is any of the previous field names (or more user-centric aliases: database for dbkey, etc.), (GUI filters as an alternate means to accomplish field specifiers to be added soon); Allow showing and hiding search input; Tweak style on panel-header buttons; pack scripts