Configurable SNORQL instance and webjar creation

1. I've changed the constructor of the SNORQL editor to accept configuration parameters such as the SPARQL endpoint.
1. I also create a pom.xml generating a webjar (to be included in webjars.org) as it simplifies the integration into other projects.

We are using SNORQL in [Apache Marmotta](http://marmotta.apache.org), currently by patching the source files. These changes would very much simplify the usage of SNORQL within Apache Marmotta and  other projects.