reorganize files

--HG--
rename : demos/cities15000.txt => demos/tools/cities15000.raw.txt
rename : demos/csv2json.php => demos/tools/csv2json.php
rename : demos/back.png => images/back.png
rename : loader.gif => images/loader.gif
rename : search-icon.png => images/search-icon.png
rename : demos/style.css => style.css