Added first stubs of MachineActions

CURA-1385

cura/MachineAction.py

@@ -0,0 +1,8 @@
+from PyQt5.QtCore import QObject
+from UM.PluginObject import PluginObject
+
+
+class MachineAction(QObject, PluginObject):
+    def __init__(self, key, label = ""):
+        self._key = key
+        self._label = label

cura/MachineActionManager.py

@@ -0,0 +1,53 @@
+from UM.Logger import Logger
+
+
+class MachineActionManager:
+    def __init__(self):
+        ##  Dict of all known machine actions
+        self._machine_actions = {}
+
+        ##  Dict of all required actions by machine reference.
+        self._required_actions = {}
+
+        ##  Dict of all supported actions by machine reference
+        self._supported_actions = {}
+
+        ##  Dict of all actions that need to be done when first added by machine reference.
+        self._first_start_actions = {}
+
+    ##  Add a required action
+    def addRequiredAction(self, machine, action_key):
+        if action_key in self._machine_actions:
+            if machine in self._required_actions:
+                self._required_actions[machine].append(action_key)
+            else:
+                self._required_actions[machine] = set(action_key)
+        else:
+            # Todo: define specific Exception types (instead of general type)
+            raise Exception("Action %s, which is required for %s is not known." % (action_key, machine.getKey()))
+
+    ##  Add a (unique) MachineAction
+    #   if the Key of the action is not unique, an exception is raised.
+    def addMachineAction(self, action):
+        if action.getKey() not in self._machine_action:
+            self._machine_action[action.getKey()] = action
+        else:
+            # Todo: define specific Exception types (instead of general type)
+            raise Exception("MachineAction with key %s was already added. Actions must have unique keys.", action.getKey())
+
+    ##  Remove Machine action from manager
+    #   \param action to remove
+    def removeMachineAction(self, action):
+        try:
+            del self._machine_actions[action.getKey()]
+        except KeyError:
+            Logger.log("w", "Trying to remove MachineAction (%s) that was already removed", action.getKey())
+
+    ##  Get MachineAction by key
+    #   \param key String of key to select
+    #   \return Machine action if found, None otherwise
+    def getMachineAction(self, key):
+        if key in self._machine_actions:
+            return self._machine_actions[key]
+        else:
+            return None