Simplified initialization of Transformation's action_kind

- Some of the Transformation classes would initialize their Action's
  action_kind using the default (using Transformation constructor
  without an action_kind parameter).
- Others, however, would use that constructor and initialize action_kind
  manually in their constructor, but setting the default value
  (RunTimeBeforeMatchAttemptKind = 1), which was redundant.
- Removed unused Transformation constructor to specify action_kind.
- Converted Action::Kind into an 'enum class' to require using the enum
  constants (instead of integer values, which are difficult to track in
  the codebase and change)

src/actions/maturity.h

@@ -30,7 +30,7 @@ namespace actions {
 class Maturity : public Action {
  public:
     explicit Maturity(const std::string &action) 
-        : Action(action, ConfigurationKind),
+        : Action(action, Kind::ConfigurationKind),
         m_maturity(0) { }
 
     bool evaluate(RuleWithActions *rule, Transaction *transaction) override;