[plot] Resetzoom not always working on right Y axis
There is an issue with reset zoom for curves on Y right axis which seems to appear when curves are moved from left to right axis

Code to reproduce:
```
from silx import sx
w = sx.plot()
w.addCurve((1, 2), (1, 10), legend='b')
w.addCurve((1, 2), (1, 2), legend='a')
for curve in w.getAllCurves():
    curve.setYAxis('right')
w.resetZoom()
```

diff --git a/silx/gui/plot/items/curve.py b/silx/gui/plot/items/curve.py
index 50ad86d7f..b67ffac7f 100644
--- a/silx/gui/plot/items/curve.py
+++ b/silx/gui/plot/items/curve.py
@@ -1,7 +1,7 @@
 # coding: utf-8
 # /*##########################################################################
 #
-# Copyright (c) 2017 European Synchrotron Radiation Facility
+# Copyright (c) 2017-2018 European Synchrotron Radiation Facility
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -70,6 +70,15 @@ class Curve(Points, ColorMixIn, YAxisMixIn, FillMixIn, LabelsMixIn, LineMixIn):
         self._highlightColor = self._DEFAULT_HIGHLIGHT_COLOR
         self._highlighted = False
 
+        self.sigItemChanged.connect(self.__itemChanged)
+
+    def __itemChanged(self, event):
+        if event == ItemChangedType.YAXIS:
+            # TODO hackish data range implementation
+            plot = self.getPlot()
+            if plot is not None:
+                plot._invalidateDataRange()
+
     def _addBackendRenderer(self, backend):
         """Update backend renderer"""
         # Filter-out values <= 0
['silx/gui/plot/items/curve.py']