refactor: common logic for "at..." triggered abilities (#13045)

* add new common framework for at step triggered abilities

* move postcombat main and second main triggers to it

* update draw step triggers

* refactor BeginningOfCombatTriggeredAbility

* refactor BeginningOfFirstMainTriggeredAbility

* move Pronoun to constants package

* cleanup some cards to use simpler constructors

* package reorganization

Mage/src/main/java/mage/constants/Pronoun.java

@@ -0,0 +1,33 @@
+package mage.constants;
+
+/**
+ * Created by IGOUDT on 5-3-2017.
+ */
+public enum Pronoun {
+    HE("he", "him", "his"),
+    SHE("she", "her", "her"),
+    THEY("they", "them", "their"),
+    IT("it", "it", "its");
+
+    private final String subjective;
+    private final String objective;
+    private final String possessive;
+
+    Pronoun(String subjective, String objective, String possessive) {
+        this.subjective = subjective;
+        this.objective = objective;
+        this.possessive = possessive;
+    }
+
+    public String getSubjective() {
+        return subjective;
+    }
+
+    public String getObjective() {
+        return objective;
+    }
+
+    public String getPossessive() {
+        return possessive;
+    }
+}