ImageDisplay can't retrieve the current position of an Axis

Steps to reproduce :
1. Open Mitosis sample
2. Change the position of the different dimensions
3. Launch this script

``` python
# @ImageDisplay img

from net.imagej.axis import Axes

print(img.getLongPosition(Axes.Z))
print(img.getLongPosition(Axes.X))
print(img.getLongPosition(Axes.Y))
print(img.getLongPosition(Axes.TIME))
print(img.getLongPosition(Axes.CHANNEL))
```

It should print `0` for all the dimensions.

I guess it's an issue with IJ1 <-> IJ2 synchronization. Should we except such methods to work or it is a limitation of running IJ2 under the IJ1 interface ?

Reproduce the issue with the Mitosis sample by changing dimension positions and running the provided Python script through ImageDisplay. Start by tracing how getLongPosition for Axes.Z, X, Y, TIME, and CHANNEL crosses the IJ1/IJ2 boundary. Done means the script reports the current positions, or the limitation is clearly established and documented.

Written by the indexing model from the issue text.