Add attributes/metadata to the KNIPImage object

[LauLauThom]

The KNIPImage object have so far only one attribute which is the array containing the pixel values. It would be nice to have the others metadata available as attributes of this object. So that we could read/write the metadata from/to the image in the KNIME tables.

One can use the metadata nodes for most cases but still that would be quite handy.
Thanks

[gab1one]

Thank you for this suggestion, we will try to include it in a future version of this plugin 👍