add laser plugin object

mythril/laser/ethereum/plugins/plugin.py

@@ -0,0 +1,23 @@
+from mythril.laser.ethereum.svm import LaserEVM
+
+
+class LaserPlugin:
+    """ Base class for laser plugins
+
+    Functionality in laser that the symbolic execution process does not need to depend on
+    can be implemented in the form of a laser plugin.
+
+    Laser plugins implement the function initialize(symbolic_vm) which is called with the laser virtual machine
+    when they are loaded.
+    Regularly a plugin will introduce several hooks into laser in this function
+
+    Plugins can direct actions by raising Signals defined in mythril.laser.ethereum.plugins.signals
+    For example, a pruning plugin might raise the PluginSkipWorldState signal.
+    """
+
+    def initialize(self, symbolic_vm: LaserEVM):
+        """ Initializes this plugin on the symbolic virtual machine
+
+        :param symbolic_vm: symbolic virtual machine to initialize the laser plugin on
+        """
+        raise NotImplementedError