Fix search box position and add search icon to it

This is how the search box looks now: https://www.dropbox.com/s/yp2hpgemupa7ype/Screenshot%202013-12-12%2013.40.41.png

This commit is messy with loads of diff. The issue is due to a new version of bootstrap which overwrote the css files with new values. Otherwise, I will have to manually edit the theme css files and paste the css code.

I manually edited the `template/jsdoc.conf.json` with the theme name and generated the css using `grunt less` for each theme (13 of them!). Can you suggest a better way? I have already asked the same question in #14.