Print detectors count on Slither CLI

This way we can see:
```
INFO:Slither:. analyzed (34 contracts with 38 detectors), 378 result(s) found
```

for public Slither version and more for the private one ;).

slither/__main__.py

@@ -617,7 +617,7 @@ def main_impl(all_detector_classes, all_printer_classes):
         if printer_classes:
             logger.info('%s analyzed (%d contracts)', filename, number_contracts)
         else:
-            logger.info('%s analyzed (%d contracts), %d result(s) found', filename, number_contracts, len(results))
+            logger.info('%s analyzed (%d contracts with %d detectors), %d result(s) found', filename, number_contracts, len(detector_classes), len(results))
         if args.ignore_return_value:
             return