Style: migration to twitter bootstrap 3

 * fast replacement - accordion, accordion-toggle deleted
 * header porting completed
 * searchbar migration
 * fixed different padding at different window widths
 * css fom page.html, header.html moved to base.css
 * layout of the search page adapted
 * footer stylization
 * portalboxes migrated to panels
 * registration, login page form migration
 * icon -> glyphicon replacement
 * account management page migrated
 * navarheader substituted with dropdown-header in a couple of places
 * search settings menu improved
 * advanced search form adapted
 * replaced all occurences of buttons-radio -> buttons
 * searchbar and search options menu improvements
 * search settings layout improved
 * makefile modified to install bootstrap3