Added CameraImageProvider & camera handling

CURA-1036 and CURA-338

cura/CameraImageProvider.py

@@ -0,0 +1,18 @@
+from PyQt5.QtGui import QImage
+from PyQt5.QtQuick import QQuickImageProvider
+from PyQt5.QtCore import QSize
+
+from UM.Application import Application
+
+class CameraImageProvider(QQuickImageProvider):
+    def __init__(self):
+        QQuickImageProvider.__init__(self, QQuickImageProvider.Image)
+
+    ##  Request a new image.
+    def requestImage(self, id, size):
+        for output_device in Application.getInstance().getOutputDeviceManager().getOutputDevices():
+            try:
+                return output_device.getCameraImage(), QSize(15, 15)
+            except AttributeError:
+                pass
+        return QImage(), QSize(15, 15)