Rewrite of Fuseki web interface

I've rewritten the Fuseki web interface.

New features:

* refactored interface to twitter bootstrap
* added yasqe and yasgui as sparql js libs, for better query formulation support
* changed welcome page from html to tpl
* changed page structure. Most importantly: consolidated different SPARQL interfaces for update and selects,  switching target dataset does not require page reload anymore, and removed data validator page, as this was not functional