CCDData translator should allow non celestial data

[astrofrog]

For example, a 2-d spectrum might be a valid CCDData. Example error:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-23-1e1b3b186e32> in <module>
      7 japp = JupyterApplication()
      8 
----> 9 japp.data_collection['test'] = spec2d
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data_collection.py in __setitem__(self, key, data)
    382             handler, preferred = data_translator.get_handler_for(data)
    383 
--> 384             data = handler.to_data(data)
    385             data._preferred_translation = preferred
    386 
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue_astronomy/translators/ccddata.py in to_data(self, obj)
     17     def to_data(self, obj):
     18         data = Data(coords=obj.wcs)
---> 19         data['data'] = obj.data
     20         data.get_component('data').units = str(obj.unit)
     21         data.meta.update(obj.meta)
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data.py in __setitem__(self, key, value)
   1391         Wrapper for data.add_component()
   1392         """
-> 1393         self.add_component(value, key)
   1394 
   1395     @contract(component_id='cid_like|None', returns=Component)
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data.py in add_component(self, component, label)
    976         if len(self._components) == 0:
    977             # TODO: make sure the following doesn't raise a componentsraised message
--> 978             self._create_pixel_and_world_components(ndim=component.ndim)
    979 
    980         # In some cases, such as when loading a session, we actually disable the
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data.py in _create_pixel_and_world_components(self, ndim)
   1110     def _create_pixel_and_world_components(self, ndim):
   1111         self._update_pixel_components(ndim)
-> 1112         self._update_world_components(ndim)
   1113 
   1114     def _update_pixel_components(self, ndim):
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data.py in _update_world_components(self, ndim)
   1139                     cid = self.add_component(comp, label)
   1140                     self._world_component_ids.append(cid)
-> 1141                 self._set_up_coordinate_component_links(ndim)
   1142 
   1143     def _set_up_coordinate_component_links(self, ndim):
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/data.py in _set_up_coordinate_component_links(self, ndim)
   1148         result = []
   1149         for i in range(ndim):
-> 1150             link = CoordinateComponentLink(self._pixel_component_ids,
   1151                                            self._world_component_ids[i],
   1152                                            self.coords, i)
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/component_link.py in __init__(self, comp_from, comp_to, coords, index, pixel2world)
    366         self._from_all = comp_from
    367 
--> 368         comp_from = [comp_from[i] for i in self.from_needed]
    369         super(CoordinateComponentLink, self).__init__(
    370             comp_from, comp_to, self.using)
​
~/anaconda3/envs/jdaviz_dev/lib/python3.8/site-packages/glue/core/component_link.py in <listcomp>(.0)
    366         self._from_all = comp_from
    367 
--> 368         comp_from = [comp_from[i] for i in self.from_needed]
    369         super(CoordinateComponentLink, self).__init__(
    370             comp_from, comp_to, self.using)
​
IndexError: list index out of range