IOPA Middleware

@class Static
@this app.properties  the IOPA AppBuilder Properties Dictionary, used to add server.capabilities
@constructor
@public
function Static(app, root, opts) {
     app.properties[SERVER.Capabilities][STATIC.CAPABILITY] = {};
     app.properties[SERVER.Capabilities][STATIC.CAPABILITY][SERVER.Version] = packageVersion;
     
      opts = opts || {};

     // options
     opts.root = root;
     opts.index = opts.index || 'index.html';
     
     return function Static_invoke(context, next) {
    
      return send(context, context[IOPA.Path], opts).then(function filesendContinuation(){
                                                      if (context.response[IOPA.StatusCode] == null)
                                                      {
                                                      context = null;
                                                      return next()
                                                      }
                                                      context = null;
                                                      });
        };
}