Minor Gantt chart improvements

* Task do not open anymore in a new window on the Gantt chart
* Do not display task progress for tasks with no start/end date

gulpfile.js

@@ -129,6 +129,7 @@ gulp.task('vendor', function() {
 gulp.task('js', function() {
     gulp.src(src.js)
         .pipe(concat('app.min.js'))
+        .pipe(uglify())
         .pipe(gulp.dest(dist.js))
     ;
 });