CrossSpectralData constructor does not accept `trialdefinition`

Other `continuous` datatype have no problems with this:
```python
spy.SpectralData(data=data, trialdefinition=trldef)

# however this fails
spy.CrossSpectralData(data=data, trialdefinition=trldef)
>>> TypeError: CrossSpectralData.__init__() got an unexpected keyword argument 'trialdefinition'
```