Add AccompanyingCourseStepHistory counting capabilities

The newly created CountAccompanyingCourseStepHistory class counts changes in AccompanyingPeriod status. Corresponding test file ensures the correct functionality. Supporting translations and necessary export declarations have been added to facilitate this change.

src/Bundle/ChillPersonBundle/Export/Declarations.php

@@ -18,6 +18,8 @@ abstract class Declarations
 {
     final public const ACP_TYPE = 'accompanying_period';
 
+    final public const ACP_STEP_HISTORY = 'accompanying_period_step_history';
+
     final public const EVAL_TYPE = 'evaluation';
 
     final public const HOUSEHOLD_TYPE = 'household';