move repr_html to _ImageWrapper

[jo-mueller]

Fixes #428

Dear OME-Team,

this PR fixes the issue that some classes that derive from BlitzObjectWrapper do not possess the necessary attributes to display the repr_html method correctly. repr_html mthods should be introduced specifically for each derived object. In this PR I simply move the repr_html to the derived class.

Since this is my last day at work before a longer parental leave, I unfortunately don't have the time to test this in detail but I hope that it's enough to get you started on the fix.

[erindiel]

Thank you @jo-mueller - I came across the same issue when working with XML Annotations, and how nice to have the issue not only already reported but a fix proposed as well.

When using conn.getObject('Annotation', annotation_id) (where conn is my BlitzGateway), my error was (same as yours):

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
~/venvs/roi.venv/lib/python3.10/site-packages/omero/gateway/__init__.py in ?(self)
    249         """
    250         Returns an HTML representation of the object. This is used by the
    251         IPython notebook to display the object in a cell.
    252         """
--> 253         return image_to_html(self)

~/venvs/roi.venv/lib/python3.10/site-packages/omero/gateway/utils.py in ?(image)
    267     <table>
    268         <tr><th></th><th>ID</th><th>Name</th></tr>
    269         {obj_html(image, 'Image')}
    270         {obj_html(image.getParent(), 'Dataset')}
--> 271         {obj_html(image.getProject(), 'Project')}
    272     </table>
    273     """
    274 

~/venvs/roi.venv/lib/python3.10/site-packages/omero/gateway/__init__.py in ?(self, attr)
   1307                             rv = rv.decode('utf8')
   1308                         except:
   1309                             pass
   1310             return rv
-> 1311         raise AttributeError(
   1312             "'%s' object has no attribute '%s'"
   1313             % (self._obj.__class__.__name__, attr))

AttributeError: 'XmlAnnotationI' object has no attribute 'getProject'

Including your changes resolved this issue and all downstream work with the resultant XmlAnnotationWrapper behaved as expected.