Improve representations for Bunch and Beam classes

mbtrack2/tracking/particles.py

@@ -160,7 +160,7 @@ class Bunch:
     
     def __repr__(self):
         """Return representation of alive particles"""
-        return f'{pd.DataFrame(self[:])!r}'
+        return f'Bunch with macro-particles: \n {pd.DataFrame(self[:])!r}'
         
     @property
     def mp_number(self):
@@ -583,7 +583,7 @@ class Beam:
     
     def __repr__(self):
         """Return representation of the beam filling pattern"""
-        return f'{list((self.filling_pattern))!r}'
+        return f'Beam with bunch current:\n {list((self.bunch_current))!r}'
    
     @property             
     def not_empty(self):