Add RemovableDrive plugin that has been moved from Uranium

Since it now depends on GCodeWriter we should put it somewhere where
GCodeWriter actually exists.

plugins/RemovableDriveOutputDevice/RemovableDrivePlugin.py

@@ -0,0 +1,73 @@
+# Copyright (c) 2015 Ultimaker B.V.
+# Uranium is released under the terms of the AGPLv3 or higher.
+
+import threading
+import time
+
+from UM.Signal import Signal
+from UM.Message import Message
+from UM.OutputDevice.OutputDevicePlugin import OutputDevicePlugin
+
+from . import RemovableDriveOutputDevice
+
+from UM.i18n import i18nCatalog
+catalog = i18nCatalog("uranium")
+
+class RemovableDrivePlugin(OutputDevicePlugin):
+    def __init__(self):
+        super().__init__()
+
+        self._update_thread = threading.Thread(target = self._updateThread)
+        self._update_thread.setDaemon(True)
+
+        self._check_updates = True
+
+        self._drives = {}
+
+    def start(self):
+        self._update_thread.start()
+
+    def stop(self):
+        self._check_updates = False
+        self._update_thread.join()
+
+        self._addRemoveDrives({})
+
+    def checkRemovableDrives(self):
+        raise NotImplementedError()
+
+    def ejectDevice(self, device):
+        result = self.performEjectDevice(device)
+        if result:
+            message = Message(catalog.i18n("Ejected {0}. You can now safely remove the drive.").format(device.getName()))
+            message.show()
+        else:
+            message = Message(catalog.i18n("Failed to eject {0}. Maybe it is still in use?").format(device.getName()))
+            message.show()
+
+    def performEjectDevice(self, device):
+        raise NotImplementedError()
+
+    def _updateThread(self):
+        while self._check_updates:
+            result = self.checkRemovableDrives()
+            self._addRemoveDrives(result)
+            time.sleep(5)
+
+    def _addRemoveDrives(self, drives):
+        # First, find and add all new or changed keys
+        for key, value in drives.items():
+            if key not in self._drives:
+                self.getOutputDeviceManager().addOutputDevice(RemovableDriveOutputDevice.RemovableDriveOutputDevice(key, value))
+                continue
+
+            if self._drives[key] != value:
+                self.getOutputDeviceManager().removeOutputDevice(key)
+                self.getOutputDeviceManager().addOutputDevice(RemovableDriveOutputDevice.RemovableDriveOutputDevice(key, value))
+
+        # Then check for keys that have been removed
+        for key in self._drives.keys():
+            if key not in drives:
+                self.getOutputDeviceManager().removeOutputDevice(key)
+
+        self._drives = drives