Added support for runtime parameters and updated dataTXT to the stable version

Before this update, the NER extension supported only global settings;
now it is possible to add runtime properties to services, which are
settings that are not global, but can change at each run (i.e. the
"confidence" parameter for the DBpediaSpotlight service).

More specifically:
- each service now accepts runtime parameters and can set their
  default value;
- in the extraction modal, the runtime parameters are shown so that
  users can change their values at each run;
- the values of the runtime parameters are also added to the
  operation in the history;
- the "Confidence" and "Support" parameters of DBPediaSpotlight
  are now runtime parameters;
- dataTXT is now updated to the new stable version, available
  on http://dandelion.eu;
- to keep backward compatibility, a setProperty will fallback
  on setRuntimePropertyDefault if the property name is not found;
- the createExtractionRequestBody now gets a Map\<String,String\>
  of the runtime parameter values given by the user.