dimensions reversing

Hi @haesleinhuepf,

when using clijx in Python at some point the array dimensions get reversed either by the ```ij.py.to_java()``` function or by the ```clijx.push``` function. See for example [this notebook](https://nbviewer.jupyter.org/github/guiwitz/clij_tests/blob/master/clij_minimal.ipynb). Of course one can swap dimensions manually, but in interest of making this easy to use, it would be nice to be able to use the default dimension ordering.
Cheers,
Guillaume