add execution info class

mythril/laser/execution_info.py

@@ -0,0 +1,11 @@
+from abc import ABC, abstractmethod
+
+
+class ExecutionInfo(ABC):
+    @abstractmethod
+    def as_dict(self):
+        """Returns a dictionary with the execution info contained in this object
+
+        The returned dictionary only uses primitive types.
+        """
+        pass