Slight tweaks for CreatureException, add tests to see if what() works.

tests/ExceptionTests.cpp

@@ -0,0 +1,15 @@
+#ifdef TESTS_BUILD
+#include <cstring>
+#include "../extern/catch.hpp"
+#include "../src/Core/Exceptions/CreatureException.hpp"
+
+TEST_CASE("When throwing exception, what() is readable", "[Utilities]") {
+    try {
+        throw CreatureException("foobar");
+    } catch (const CreatureException& e) {
+        INFO(e.what());
+        REQUIRE(strcmp(e.what(), "foobar") == 0);
+    }
+}
+
+#endif