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/set_uid.h

@@ -36,7 +36,7 @@ class SetUID : public Action {
         : Action(_action) { }
 
     explicit SetUID(std::unique_ptr<RunTimeString> z)
-        : Action("setuid", RunTimeOnlyIfMatchKind),
+        : Action("setuid"),
             m_string(std::move(z)) { }
 
     bool evaluate(RuleWithActions *rule, Transaction *transaction) override;